fs/exec.c

   1 /*
   2  *  linux/fs/exec.c
   3  *
   4  *  Copyright (C) 1991, 1992  Linus Torvalds
   5  */
   6
   7 /*
   8  * #!-checking implemented by tytso.
   9  */
  10 /*
  11  * Demand-loading implemented 01.12.91 - no need to read anything but
  12  * the header into memory. The inode of the executable is put into
  13  * "current->executable", and page faults do the actual loading. Clean.
  14  *
  15  * Once more I can proudly say that linux stood up to being changed: it
  16  * was less than 2 hours work to get demand-loading completely implemented.
  17  *
  18  * Demand loading changed July 1993 by Eric Youngdale.   Use mmap instead,
  19  * current->executable is only used by the procfs.  This allows a dispatch
  20  * table to check for several different types  of binary formats.  We keep
  21  * trying until we recognize the file or we run out of supported binary
  22  * formats.
  23  */
  24
  25 #include <linux/slab.h>
  26 #include <linux/file.h>
  27 #include <linux/fdtable.h>
  28 #include <linux/mm.h>
  29 #include <linux/stat.h>
  30 #include <linux/fcntl.h>
  31 #include <linux/swap.h>
  32 #include <linux/string.h>
  33 #include <linux/init.h>
  34 #include <linux/pagemap.h>
  35 #include <linux/perf_event.h>
  36 #include <linux/highmem.h>
  37 #include <linux/spinlock.h>
  38 #include <linux/key.h>
  39 #include <linux/personality.h>
  40 #include <linux/binfmts.h>
  41 #include <linux/utsname.h>
  42 #include <linux/pid_namespace.h>
  43 #include <linux/module.h>
  44 #include <linux/namei.h>
  45 #include <linux/mount.h>
  46 #include <linux/security.h>
  47 #include <linux/syscalls.h>
  48 #include <linux/tsacct_kern.h>
  49 #include <linux/cn_proc.h>
  50 #include <linux/audit.h>
  51 #include <linux/tracehook.h>
  52 #include <linux/kmod.h>
  53 #include <linux/fsnotify.h>
  54 #include <linux/fs_struct.h>
  55 #include <linux/pipe_fs_i.h>
  56 #include <linux/oom.h>
  57 #include <linux/compat.h>
  58
  59 #include <asm/uaccess.h>
  60 #include <asm/mmu_context.h>
  61 #include <asm/tlb.h>
  62 #include "internal.h"
  63
  64 int core_uses_pid;
  65 char core_pattern[CORENAME_MAX_SIZE] = "core";
  66 unsigned int core_pipe_limit;
  67 int suid_dumpable = 0;
  68
  69 struct core_name {
  70         char *corename;
  71         int used, size;
  72 };
  73 static atomic_t call_count = ATOMIC_INIT(1);
  74
  75 /* The maximal length of core_pattern is also specified in sysctl.c */
  76
  77 static LIST_HEAD(formats);
  78 static DEFINE_RWLOCK(binfmt_lock);
  79
  80 int __register_binfmt(struct linux_binfmt * fmt, int insert)
  81 {
  82         if (!fmt)
  83                 return -EINVAL;
  84         write_lock(&binfmt_lock);
  85         insert ? list_add(&fmt->lh, &formats) :
  86                  list_add_tail(&fmt->lh, &formats);
  87         write_unlock(&binfmt_lock);
  88         return 0;
  89 }
  90
  91 EXPORT_SYMBOL(__register_binfmt);
  92
  93 void unregister_binfmt(struct linux_binfmt * fmt)
  94 {
  95         write_lock(&binfmt_lock);
  96         list_del(&fmt->lh);
  97         write_unlock(&binfmt_lock);
  98 }
  99
 100 EXPORT_SYMBOL(unregister_binfmt);
 101
 102 static inline void put_binfmt(struct linux_binfmt * fmt)
 103 {
 104         module_put(fmt->module);
 105 }
 106
 107 /*
 108  * Note that a shared library must be both readable and executable due to
 109  * security reasons.
 110  *
 111  * Also note that we take the address to load from from the file itself.
 112  */
 113 SYSCALL_DEFINE1(uselib, const char __user *, library)
 114 {
 115         struct file *file;
 116         char *tmp = getname(library);
 117         int error = PTR_ERR(tmp);
 118         static const struct open_flags uselib_flags = {
 119                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 120                 .acc_mode = MAY_READ | MAY_EXEC | MAY_OPEN,
 121                 .intent = LOOKUP_OPEN
 122         };
 123
 124         if (IS_ERR(tmp))
 125                 goto out;
 126
 127         file = do_filp_open(AT_FDCWD, tmp, &uselib_flags, LOOKUP_FOLLOW);
 128         putname(tmp);
 129         error = PTR_ERR(file);
 130         if (IS_ERR(file))
 131                 goto out;
 132
 133         error = -EINVAL;
 134         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 135                 goto exit;
 136
 137         error = -EACCES;
 138         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 139                 goto exit;
 140
 141         fsnotify_open(file);
 142
 143         error = -ENOEXEC;
 144         if(file->f_op) {
 145                 struct linux_binfmt * fmt;
 146
 147                 read_lock(&binfmt_lock);
 148                 list_for_each_entry(fmt, &formats, lh) {
 149                         if (!fmt->load_shlib)
 150                                 continue;
 151                         if (!try_module_get(fmt->module))
 152                                 continue;
 153                         read_unlock(&binfmt_lock);
 154                         error = fmt->load_shlib(file);
 155                         read_lock(&binfmt_lock);
 156                         put_binfmt(fmt);
 157                         if (error != -ENOEXEC)
 158                                 break;
 159                 }
 160                 read_unlock(&binfmt_lock);
 161         }
 162 exit:
 163         fput(file);
 164 out:
 165         return error;
 166 }
 167
 168 #ifdef CONFIG_MMU
 169 /*
 170  * The nascent bprm->mm is not visible until exec_mmap() but it can
 171  * use a lot of memory, account these pages in current->mm temporary
 172  * for oom_badness()->get_mm_rss(). Once exec succeeds or fails, we
 173  * change the counter back via acct_arg_size(0).
 174  */
 175 static void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 176 {
 177         struct mm_struct *mm = current->mm;
 178         long diff = (long)(pages - bprm->vma_pages);
 179
 180         if (!mm || !diff)
 181                 return;
 182
 183         bprm->vma_pages = pages;
 184
 185 #ifdef SPLIT_RSS_COUNTING
 186         add_mm_counter(mm, MM_ANONPAGES, diff);
 187 #else
 188         spin_lock(&mm->page_table_lock);
 189         add_mm_counter(mm, MM_ANONPAGES, diff);
 190         spin_unlock(&mm->page_table_lock);
 191 #endif
 192 }
 193
 194 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 195                 int write)
 196 {
 197         struct page *page;
 198         int ret;
 199
 200 #ifdef CONFIG_STACK_GROWSUP
 201         if (write) {
 202                 ret = expand_downwards(bprm->vma, pos);
 203                 if (ret < 0)
 204                         return NULL;
 205         }
 206 #endif
 207         ret = get_user_pages(current, bprm->mm, pos,
 208                         1, write, 1, &page, NULL);
 209         if (ret <= 0)
 210                 return NULL;
 211
 212         if (write) {
 213                 unsigned long size = bprm->vma->vm_end - bprm->vma->vm_start;
 214                 struct rlimit *rlim;
 215
 216                 acct_arg_size(bprm, size / PAGE_SIZE);
 217
 218                 /*
 219                  * We've historically supported up to 32 pages (ARG_MAX)
 220                  * of argument strings even with small stacks
 221                  */
 222                 if (size <= ARG_MAX)
 223                         return page;
 224
 225                 /*
 226                  * Limit to 1/4-th the stack size for the argv+env strings.
 227                  * This ensures that:
 228                  *  - the remaining binfmt code will not run out of stack space,
 229                  *  - the program will have a reasonable amount of stack left
 230                  *    to work from.
 231                  */
 232                 rlim = current->signal->rlim;
 233                 if (size > ACCESS_ONCE(rlim[RLIMIT_STACK].rlim_cur) / 4) {
 234                         put_page(page);
 235                         return NULL;
 236                 }
 237         }
 238
 239         return page;
 240 }
 241
 242 static void put_arg_page(struct page *page)
 243 {
 244         put_page(page);
 245 }
 246
 247 static void free_arg_page(struct linux_binprm *bprm, int i)
 248 {
 249 }
 250
 251 static void free_arg_pages(struct linux_binprm *bprm)
 252 {
 253 }
 254
 255 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 256                 struct page *page)
 257 {
 258         flush_cache_page(bprm->vma, pos, page_to_pfn(page));
 259 }
 260
 261 static int __bprm_mm_init(struct linux_binprm *bprm)
 262 {
 263         int err;
 264         struct vm_area_struct *vma = NULL;
 265         struct mm_struct *mm = bprm->mm;
 266
 267         bprm->vma = vma = kmem_cache_zalloc(vm_area_cachep, GFP_KERNEL);
 268         if (!vma)
 269                 return -ENOMEM;
 270
 271         down_write(&mm->mmap_sem);
 272         vma->vm_mm = mm;
 273
 274         /*
 275          * Place the stack at the largest stack address the architecture
 276          * supports. Later, we'll move this to an appropriate place. We don't
 277          * use STACK_TOP because that can depend on attributes which aren't
 278          * configured yet.
 279          */
 280         BUG_ON(VM_STACK_FLAGS & VM_STACK_INCOMPLETE_SETUP);
 281         vma->vm_end = STACK_TOP_MAX;
 282         vma->vm_start = vma->vm_end - PAGE_SIZE;
 283         vma->vm_flags = VM_STACK_FLAGS | VM_STACK_INCOMPLETE_SETUP;
 284         vma->vm_page_prot = vm_get_page_prot(vma->vm_flags);
 285         INIT_LIST_HEAD(&vma->anon_vma_chain);
 286
 287         err = security_file_mmap(NULL, 0, 0, 0, vma->vm_start, 1);
 288         if (err)
 289                 goto err;
 290
 291         err = insert_vm_struct(mm, vma);
 292         if (err)
 293                 goto err;
 294
 295         mm->stack_vm = mm->total_vm = 1;
 296         up_write(&mm->mmap_sem);
 297         bprm->p = vma->vm_end - sizeof(void *);
 298         return 0;
 299 err:
 300         up_write(&mm->mmap_sem);
 301         bprm->vma = NULL;
 302         kmem_cache_free(vm_area_cachep, vma);
 303         return err;
 304 }
 305
 306 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 307 {
 308         return len <= MAX_ARG_STRLEN;
 309 }
 310
 311 #else
 312
 313 static inline void acct_arg_size(struct linux_binprm *bprm, unsigned long pages)
 314 {
 315 }
 316
 317 static struct page *get_arg_page(struct linux_binprm *bprm, unsigned long pos,
 318                 int write)
 319 {
 320         struct page *page;
 321
 322         page = bprm->page[pos / PAGE_SIZE];
 323         if (!page && write) {
 324                 page = alloc_page(GFP_HIGHUSER|__GFP_ZERO);
 325                 if (!page)
 326                         return NULL;
 327                 bprm->page[pos / PAGE_SIZE] = page;
 328         }
 329
 330         return page;
 331 }
 332
 333 static void put_arg_page(struct page *page)
 334 {
 335 }
 336
 337 static void free_arg_page(struct linux_binprm *bprm, int i)
 338 {
 339         if (bprm->page[i]) {
 340                 __free_page(bprm->page[i]);
 341                 bprm->page[i] = NULL;
 342         }
 343 }
 344
 345 static void free_arg_pages(struct linux_binprm *bprm)
 346 {
 347         int i;
 348
 349         for (i = 0; i < MAX_ARG_PAGES; i++)
 350                 free_arg_page(bprm, i);
 351 }
 352
 353 static void flush_arg_page(struct linux_binprm *bprm, unsigned long pos,
 354                 struct page *page)
 355 {
 356 }
 357
 358 static int __bprm_mm_init(struct linux_binprm *bprm)
 359 {
 360         bprm->p = PAGE_SIZE * MAX_ARG_PAGES - sizeof(void *);
 361         return 0;
 362 }
 363
 364 static bool valid_arg_len(struct linux_binprm *bprm, long len)
 365 {
 366         return len <= bprm->p;
 367 }
 368
 369 #endif /* CONFIG_MMU */
 370
 371 /*
 372  * Create a new mm_struct and populate it with a temporary stack
 373  * vm_area_struct.  We don't have enough context at this point to set the stack
 374  * flags, permissions, and offset, so we use temporary values.  We'll update
 375  * them later in setup_arg_pages().
 376  */
 377 int bprm_mm_init(struct linux_binprm *bprm)
 378 {
 379         int err;
 380         struct mm_struct *mm = NULL;
 381
 382         bprm->mm = mm = mm_alloc();
 383         err = -ENOMEM;
 384         if (!mm)
 385                 goto err;
 386
 387         err = init_new_context(current, mm);
 388         if (err)
 389                 goto err;
 390
 391         err = __bprm_mm_init(bprm);
 392         if (err)
 393                 goto err;
 394
 395         return 0;
 396
 397 err:
 398         if (mm) {
 399                 bprm->mm = NULL;
 400                 mmdrop(mm);
 401         }
 402
 403         return err;
 404 }
 405
 406 struct user_arg_ptr {
 407 #ifdef CONFIG_COMPAT
 408         bool is_compat;
 409 #endif
 410         union {
 411                 const char __user *const __user *native;
 412 #ifdef CONFIG_COMPAT
 413                 compat_uptr_t __user *compat;
 414 #endif
 415         } ptr;
 416 };
 417
 418 static const char __user *get_user_arg_ptr(struct user_arg_ptr argv, int nr)
 419 {
 420         const char __user *native;
 421
 422 #ifdef CONFIG_COMPAT
 423         if (unlikely(argv.is_compat)) {
 424                 compat_uptr_t compat;
 425
 426                 if (get_user(compat, argv.ptr.compat + nr))
 427                         return ERR_PTR(-EFAULT);
 428
 429                 return compat_ptr(compat);
 430         }
 431 #endif
 432
 433         if (get_user(native, argv.ptr.native + nr))
 434                 return ERR_PTR(-EFAULT);
 435
 436         return native;
 437 }
 438
 439 /*
 440  * count() counts the number of strings in array ARGV.
 441  */
 442 static int count(struct user_arg_ptr argv, int max)
 443 {
 444         int i = 0;
 445
 446         if (argv.ptr.native != NULL) {
 447                 for (;;) {
 448                         const char __user *p = get_user_arg_ptr(argv, i);
 449
 450                         if (!p)
 451                                 break;
 452
 453                         if (IS_ERR(p))
 454                                 return -EFAULT;
 455
 456                         if (i++ >= max)
 457                                 return -E2BIG;
 458
 459                         if (fatal_signal_pending(current))
 460                                 return -ERESTARTNOHAND;
 461                         cond_resched();
 462                 }
 463         }
 464         return i;
 465 }
 466
 467 /*
 468  * 'copy_strings()' copies argument/environment strings from the old
 469  * processes's memory to the new process's stack.  The call to get_user_pages()
 470  * ensures the destination page is created and not swapped out.
 471  */
 472 static int copy_strings(int argc, struct user_arg_ptr argv,
 473                         struct linux_binprm *bprm)
 474 {
 475         struct page *kmapped_page = NULL;
 476         char *kaddr = NULL;
 477         unsigned long kpos = 0;
 478         int ret;
 479
 480         while (argc-- > 0) {
 481                 const char __user *str;
 482                 int len;
 483                 unsigned long pos;
 484
 485                 ret = -EFAULT;
 486                 str = get_user_arg_ptr(argv, argc);
 487                 if (IS_ERR(str))
 488                         goto out;
 489
 490                 len = strnlen_user(str, MAX_ARG_STRLEN);
 491                 if (!len)
 492                         goto out;
 493
 494                 ret = -E2BIG;
 495                 if (!valid_arg_len(bprm, len))
 496                         goto out;
 497
 498                 /* We're going to work our way backwords. */
 499                 pos = bprm->p;
 500                 str += len;
 501                 bprm->p -= len;
 502
 503                 while (len > 0) {
 504                         int offset, bytes_to_copy;
 505
 506                         if (fatal_signal_pending(current)) {
 507                                 ret = -ERESTARTNOHAND;
 508                                 goto out;
 509                         }
 510                         cond_resched();
 511
 512                         offset = pos % PAGE_SIZE;
 513                         if (offset == 0)
 514                                 offset = PAGE_SIZE;
 515
 516                         bytes_to_copy = offset;
 517                         if (bytes_to_copy > len)
 518                                 bytes_to_copy = len;
 519
 520                         offset -= bytes_to_copy;
 521                         pos -= bytes_to_copy;
 522                         str -= bytes_to_copy;
 523                         len -= bytes_to_copy;
 524
 525                         if (!kmapped_page || kpos != (pos & PAGE_MASK)) {
 526                                 struct page *page;
 527
 528                                 page = get_arg_page(bprm, pos, 1);
 529                                 if (!page) {
 530                                         ret = -E2BIG;
 531                                         goto out;
 532                                 }
 533
 534                                 if (kmapped_page) {
 535                                         flush_kernel_dcache_page(kmapped_page);
 536                                         kunmap(kmapped_page);
 537                                         put_arg_page(kmapped_page);
 538                                 }
 539                                 kmapped_page = page;
 540                                 kaddr = kmap(kmapped_page);
 541                                 kpos = pos & PAGE_MASK;
 542                                 flush_arg_page(bprm, kpos, kmapped_page);
 543                         }
 544                         if (copy_from_user(kaddr+offset, str, bytes_to_copy)) {
 545                                 ret = -EFAULT;
 546                                 goto out;
 547                         }
 548                 }
 549         }
 550         ret = 0;
 551 out:
 552         if (kmapped_page) {
 553                 flush_kernel_dcache_page(kmapped_page);
 554                 kunmap(kmapped_page);
 555                 put_arg_page(kmapped_page);
 556         }
 557         return ret;
 558 }
 559
 560 /*
 561  * Like copy_strings, but get argv and its values from kernel memory.
 562  */
 563 int copy_strings_kernel(int argc, const char *const *__argv,
 564                         struct linux_binprm *bprm)
 565 {
 566         int r;
 567         mm_segment_t oldfs = get_fs();
 568         struct user_arg_ptr argv = {
 569                 .ptr.native = (const char __user *const  __user *)__argv,
 570         };
 571
 572         set_fs(KERNEL_DS);
 573         r = copy_strings(argc, argv, bprm);
 574         set_fs(oldfs);
 575
 576         return r;
 577 }
 578 EXPORT_SYMBOL(copy_strings_kernel);
 579
 580 #ifdef CONFIG_MMU
 581
 582 /*
 583  * During bprm_mm_init(), we create a temporary stack at STACK_TOP_MAX.  Once
 584  * the binfmt code determines where the new stack should reside, we shift it to
 585  * its final location.  The process proceeds as follows:
 586  *
 587  * 1) Use shift to calculate the new vma endpoints.
 588  * 2) Extend vma to cover both the old and new ranges.  This ensures the
 589  *    arguments passed to subsequent functions are consistent.
 590  * 3) Move vma's page tables to the new range.
 591  * 4) Free up any cleared pgd range.
 592  * 5) Shrink the vma to cover only the new range.
 593  */
 594 static int shift_arg_pages(struct vm_area_struct *vma, unsigned long shift)
 595 {
 596         struct mm_struct *mm = vma->vm_mm;
 597         unsigned long old_start = vma->vm_start;
 598         unsigned long old_end = vma->vm_end;
 599         unsigned long length = old_end - old_start;
 600         unsigned long new_start = old_start - shift;
 601         unsigned long new_end = old_end - shift;
 602         struct mmu_gather tlb;
 603
 604         BUG_ON(new_start > new_end);
 605
 606         /*
 607          * ensure there are no vmas between where we want to go
 608          * and where we are
 609          */
 610         if (vma != find_vma(mm, new_start))
 611                 return -EFAULT;
 612
 613         /*
 614          * cover the whole range: [new_start, old_end)
 615          */
 616         if (vma_adjust(vma, new_start, old_end, vma->vm_pgoff, NULL))
 617                 return -ENOMEM;
 618
 619         /*
 620          * move the page tables downwards, on failure we rely on
 621          * process cleanup to remove whatever mess we made.
 622          */
 623         if (length != move_page_tables(vma, old_start,
 624                                        vma, new_start, length))
 625                 return -ENOMEM;
 626
 627         lru_add_drain();
 628         tlb_gather_mmu(&tlb, mm, 0);
 629         if (new_end > old_start) {
 630                 /*
 631                  * when the old and new regions overlap clear from new_end.
 632                  */
 633                 free_pgd_range(&tlb, new_end, old_end, new_end,
 634                         vma->vm_next ? vma->vm_next->vm_start : 0);
 635         } else {
 636                 /*
 637                  * otherwise, clean from old_start; this is done to not touch
 638                  * the address space in [new_end, old_start) some architectures
 639                  * have constraints on va-space that make this illegal (IA64) -
 640                  * for the others its just a little faster.
 641                  */
 642                 free_pgd_range(&tlb, old_start, old_end, new_end,
 643                         vma->vm_next ? vma->vm_next->vm_start : 0);
 644         }
 645         tlb_finish_mmu(&tlb, new_end, old_end);
 646
 647         /*
 648          * Shrink the vma to just the new range.  Always succeeds.
 649          */
 650         vma_adjust(vma, new_start, new_end, vma->vm_pgoff, NULL);
 651
 652         return 0;
 653 }
 654
 655 /*
 656  * Finalizes the stack vm_area_struct. The flags and permissions are updated,
 657  * the stack is optionally relocated, and some extra space is added.
 658  */
 659 int setup_arg_pages(struct linux_binprm *bprm,
 660                     unsigned long stack_top,
 661                     int executable_stack)
 662 {
 663         unsigned long ret;
 664         unsigned long stack_shift;
 665         struct mm_struct *mm = current->mm;
 666         struct vm_area_struct *vma = bprm->vma;
 667         struct vm_area_struct *prev = NULL;
 668         unsigned long vm_flags;
 669         unsigned long stack_base;
 670         unsigned long stack_size;
 671         unsigned long stack_expand;
 672         unsigned long rlim_stack;
 673
 674 #ifdef CONFIG_STACK_GROWSUP
 675         /* Limit stack size to 1GB */
 676         stack_base = rlimit_max(RLIMIT_STACK);
 677         if (stack_base > (1 << 30))
 678                 stack_base = 1 << 30;
 679
 680         /* Make sure we didn't let the argument array grow too large. */
 681         if (vma->vm_end - vma->vm_start > stack_base)
 682                 return -ENOMEM;
 683
 684         stack_base = PAGE_ALIGN(stack_top - stack_base);
 685
 686         stack_shift = vma->vm_start - stack_base;
 687         mm->arg_start = bprm->p - stack_shift;
 688         bprm->p = vma->vm_end - stack_shift;
 689 #else
 690         stack_top = arch_align_stack(stack_top);
 691         stack_top = PAGE_ALIGN(stack_top);
 692
 693         if (unlikely(stack_top < mmap_min_addr) ||
 694             unlikely(vma->vm_end - vma->vm_start >= stack_top - mmap_min_addr))
 695                 return -ENOMEM;
 696
 697         stack_shift = vma->vm_end - stack_top;
 698
 699         bprm->p -= stack_shift;
 700         mm->arg_start = bprm->p;
 701 #endif
 702
 703         if (bprm->loader)
 704                 bprm->loader -= stack_shift;
 705         bprm->exec -= stack_shift;
 706
 707         down_write(&mm->mmap_sem);
 708         vm_flags = VM_STACK_FLAGS;
 709
 710         /*
 711          * Adjust stack execute permissions; explicitly enable for
 712          * EXSTACK_ENABLE_X, disable for EXSTACK_DISABLE_X and leave alone
 713          * (arch default) otherwise.
 714          */
 715         if (unlikely(executable_stack == EXSTACK_ENABLE_X))
 716                 vm_flags |= VM_EXEC;
 717         else if (executable_stack == EXSTACK_DISABLE_X)
 718                 vm_flags &= ~VM_EXEC;
 719         vm_flags |= mm->def_flags;
 720         vm_flags |= VM_STACK_INCOMPLETE_SETUP;
 721
 722         ret = mprotect_fixup(vma, &prev, vma->vm_start, vma->vm_end,
 723                         vm_flags);
 724         if (ret)
 725                 goto out_unlock;
 726         BUG_ON(prev != vma);
 727
 728         /* Move stack pages down in memory. */
 729         if (stack_shift) {
 730                 ret = shift_arg_pages(vma, stack_shift);
 731                 if (ret)
 732                         goto out_unlock;
 733         }
 734
 735         /* mprotect_fixup is overkill to remove the temporary stack flags */
 736         vma->vm_flags &= ~VM_STACK_INCOMPLETE_SETUP;
 737
 738         stack_expand = 131072UL; /* randomly 32*4k (or 2*64k) pages */
 739         stack_size = vma->vm_end - vma->vm_start;
 740         /*
 741          * Align this down to a page boundary as expand_stack
 742          * will align it up.
 743          */
 744         rlim_stack = rlimit(RLIMIT_STACK) & PAGE_MASK;
 745 #ifdef CONFIG_STACK_GROWSUP
 746         if (stack_size + stack_expand > rlim_stack)
 747                 stack_base = vma->vm_start + rlim_stack;
 748         else
 749                 stack_base = vma->vm_end + stack_expand;
 750 #else
 751         if (stack_size + stack_expand > rlim_stack)
 752                 stack_base = vma->vm_end - rlim_stack;
 753         else
 754                 stack_base = vma->vm_start - stack_expand;
 755 #endif
 756         current->mm->start_stack = bprm->p;
 757         ret = expand_stack(vma, stack_base);
 758         if (ret)
 759                 ret = -EFAULT;
 760
 761 out_unlock:
 762         up_write(&mm->mmap_sem);
 763         return ret;
 764 }
 765 EXPORT_SYMBOL(setup_arg_pages);
 766
 767 #endif /* CONFIG_MMU */
 768
 769 struct file *open_exec(const char *name)
 770 {
 771         struct file *file;
 772         int err;
 773         static const struct open_flags open_exec_flags = {
 774                 .open_flag = O_LARGEFILE | O_RDONLY | __FMODE_EXEC,
 775                 .acc_mode = MAY_EXEC | MAY_OPEN,
 776                 .intent = LOOKUP_OPEN
 777         };
 778
 779         file = do_filp_open(AT_FDCWD, name, &open_exec_flags, LOOKUP_FOLLOW);
 780         if (IS_ERR(file))
 781                 goto out;
 782
 783         err = -EACCES;
 784         if (!S_ISREG(file->f_path.dentry->d_inode->i_mode))
 785                 goto exit;
 786
 787         if (file->f_path.mnt->mnt_flags & MNT_NOEXEC)
 788                 goto exit;
 789
 790         fsnotify_open(file);
 791
 792         err = deny_write_access(file);
 793         if (err)
 794                 goto exit;
 795
 796 out:
 797         return file;
 798
 799 exit:
 800         fput(file);
 801         return ERR_PTR(err);
 802 }
 803 EXPORT_SYMBOL(open_exec);
 804
 805 int kernel_read(struct file *file, loff_t offset,
 806                 char *addr, unsigned long count)
 807 {
 808         mm_segment_t old_fs;
 809         loff_t pos = offset;
 810         int result;
 811
 812         old_fs = get_fs();
 813         set_fs(get_ds());
 814         /* The cast to a user pointer is valid due to the set_fs() */
 815         result = vfs_read(file, (void __user *)addr, count, &pos);
 816         set_fs(old_fs);
 817         return result;
 818 }
 819
 820 EXPORT_SYMBOL(kernel_read);
 821
 822 static int exec_mmap(struct mm_struct *mm)
 823 {
 824         struct task_struct *tsk;
 825         struct mm_struct * old_mm, *active_mm;
 826
 827         /* Notify parent that we're no longer interested in the old VM */
 828         tsk = current;
 829         old_mm = current->mm;
 830         sync_mm_rss(tsk, old_mm);
 831         mm_release(tsk, old_mm);
 832
 833         if (old_mm) {
 834                 /*
 835                  * Make sure that if there is a core dump in progress
 836                  * for the old mm, we get out and die instead of going
 837                  * through with the exec.  We must hold mmap_sem around
 838                  * checking core_state and changing tsk->mm.
 839                  */
 840                 down_read(&old_mm->mmap_sem);
 841                 if (unlikely(old_mm->core_state)) {
 842                         up_read(&old_mm->mmap_sem);
 843                         return -EINTR;
 844                 }
 845         }
 846         task_lock(tsk);
 847         active_mm = tsk->active_mm;
 848         tsk->mm = mm;
 849         tsk->active_mm = mm;
 850         activate_mm(active_mm, mm);
 851         if (old_mm && tsk->signal->oom_score_adj == OOM_SCORE_ADJ_MIN) {
 852                 atomic_dec(&old_mm->oom_disable_count);
 853                 atomic_inc(&tsk->mm->oom_disable_count);
 854         }
 855         task_unlock(tsk);
 856         arch_pick_mmap_layout(mm);
 857         if (old_mm) {
 858                 up_read(&old_mm->mmap_sem);
 859                 BUG_ON(active_mm != old_mm);
 860                 mm_update_next_owner(old_mm);
 861                 mmput(old_mm);
 862                 return 0;
 863         }
 864         mmdrop(active_mm);
 865         return 0;
 866 }
 867
 868 /*
 869  * This function makes sure the current process has its own signal table,
 870  * so that flush_signal_handlers can later reset the handlers without
 871  * disturbing other processes.  (Other processes might share the signal
 872  * table via the CLONE_SIGHAND option to clone().)
 873  */
 874 static int de_thread(struct task_struct *tsk)
 875 {
 876         struct signal_struct *sig = tsk->signal;
 877         struct sighand_struct *oldsighand = tsk->sighand;
 878         spinlock_t *lock = &oldsighand->siglock;
 879
 880         if (thread_group_empty(tsk))
 881                 goto no_thread_group;
 882
 883         /*
 884          * Kill all other threads in the thread group.
 885          */
 886         spin_lock_irq(lock);
 887         if (signal_group_exit(sig)) {
 888                 /*
 889                  * Another group action in progress, just
 890                  * return so that the signal is processed.
 891                  */
 892                 spin_unlock_irq(lock);
 893                 return -EAGAIN;
 894         }
 895
 896         sig->group_exit_task = tsk;
 897         sig->notify_count = zap_other_threads(tsk);
 898         if (!thread_group_leader(tsk))
 899                 sig->notify_count--;
 900
 901         while (sig->notify_count) {
 902                 __set_current_state(TASK_UNINTERRUPTIBLE);
 903                 spin_unlock_irq(lock);
 904                 schedule();
 905                 spin_lock_irq(lock);
 906         }
 907         spin_unlock_irq(lock);
 908
 909         /*
 910          * At this point all other threads have exited, all we have to
 911          * do is to wait for the thread group leader to become inactive,
 912          * and to assume its PID:
 913          */
 914         if (!thread_group_leader(tsk)) {
 915                 struct task_struct *leader = tsk->group_leader;
 916
 917                 sig->notify_count = -1; /* for exit_notify() */
 918                 for (;;) {
 919                         write_lock_irq(&tasklist_lock);
 920                         if (likely(leader->exit_state))
 921                                 break;
 922                         __set_current_state(TASK_UNINTERRUPTIBLE);
 923                         write_unlock_irq(&tasklist_lock);
 924                         schedule();
 925                 }
 926
 927                 /*
 928                  * The only record we have of the real-time age of a
 929                  * process, regardless of execs it's done, is start_time.
 930                  * All the past CPU time is accumulated in signal_struct
 931                  * from sister threads now dead.  But in this non-leader
 932                  * exec, nothing survives from the original leader thread,
 933                  * whose birth marks the true age of this process now.
 934                  * When we take on its identity by switching to its PID, we
 935                  * also take its birthdate (always earlier than our own).
 936                  */
 937                 tsk->start_time = leader->start_time;
 938
 939                 BUG_ON(!same_thread_group(leader, tsk));
 940                 BUG_ON(has_group_leader_pid(tsk));
 941                 /*
 942                  * An exec() starts a new thread group with the
 943                  * TGID of the previous thread group. Rehash the
 944                  * two threads with a switched PID, and release
 945                  * the former thread group leader:
 946                  */
 947
 948                 /* Become a process group leader with the old leader's pid.
 949                  * The old leader becomes a thread of the this thread group.
 950                  * Note: The old leader also uses this pid until release_task
 951                  *       is called.  Odd but simple and correct.
 952                  */
 953                 detach_pid(tsk, PIDTYPE_PID);
 954                 tsk->pid = leader->pid;
 955                 attach_pid(tsk, PIDTYPE_PID,  task_pid(leader));
 956                 transfer_pid(leader, tsk, PIDTYPE_PGID);
 957                 transfer_pid(leader, tsk, PIDTYPE_SID);
 958
 959                 list_replace_rcu(&leader->tasks, &tsk->tasks);
 960                 list_replace_init(&leader->sibling, &tsk->sibling);
 961
 962                 tsk->group_leader = tsk;
 963                 leader->group_leader = tsk;
 964
 965                 tsk->exit_signal = SIGCHLD;
 966
 967                 BUG_ON(leader->exit_state != EXIT_ZOMBIE);
 968                 leader->exit_state = EXIT_DEAD;
 969                 write_unlock_irq(&tasklist_lock);
 970
 971                 release_task(leader);
 972         }
 973
 974         sig->group_exit_task = NULL;
 975         sig->notify_count = 0;
 976
 977 no_thread_group:
 978         if (current->mm)
 979                 setmax_mm_hiwater_rss(&sig->maxrss, current->mm);
 980
 981         exit_itimers(sig);
 982         flush_itimer_signals();
 983
 984         if (atomic_read(&oldsighand->count) != 1) {
 985                 struct sighand_struct *newsighand;
 986                 /*
 987                  * This ->sighand is shared with the CLONE_SIGHAND
 988                  * but not CLONE_THREAD task, switch to the new one.
 989                  */
 990                 newsighand = kmem_cache_alloc(sighand_cachep, GFP_KERNEL);
 991                 if (!newsighand)
 992                         return -ENOMEM;
 993
 994                 atomic_set(&newsighand->count, 1);
 995                 memcpy(newsighand->action, oldsighand->action,
 996                        sizeof(newsighand->action));
 997
 998                 write_lock_irq(&tasklist_lock);
 999                 spin_lock(&oldsighand->siglock);
1000                 rcu_assign_pointer(tsk->sighand, newsighand);
1001                 spin_unlock(&oldsighand->siglock);
1002                 write_unlock_irq(&tasklist_lock);
1003
1004                 __cleanup_sighand(oldsighand);
1005         }
1006
1007         BUG_ON(!thread_group_leader(tsk));
1008         return 0;
1009 }
1010
1011 /*
1012  * These functions flushes out all traces of the currently running executable
1013  * so that a new one can be started
1014  */
1015 static void flush_old_files(struct files_struct * files)
1016 {
1017         long j = -1;
1018         struct fdtable *fdt;
1019
1020         spin_lock(&files->file_lock);
1021         for (;;) {
1022                 unsigned long set, i;
1023
1024                 j++;
1025                 i = j * __NFDBITS;
1026                 fdt = files_fdtable(files);
1027                 if (i >= fdt->max_fds)
1028                         break;
1029                 set = fdt->close_on_exec->fds_bits[j];
1030                 if (!set)
1031                         continue;
1032                 fdt->close_on_exec->fds_bits[j] = 0;
1033                 spin_unlock(&files->file_lock);
1034                 for ( ; set ; i++,set >>= 1) {
1035                         if (set & 1) {
1036                                 sys_close(i);
1037                         }
1038                 }
1039                 spin_lock(&files->file_lock);
1040
1041         }
1042         spin_unlock(&files->file_lock);
1043 }
1044
1045 char *get_task_comm(char *buf, struct task_struct *tsk)
1046 {
1047         /* buf must be at least sizeof(tsk->comm) in size */
1048         task_lock(tsk);
1049         strncpy(buf, tsk->comm, sizeof(tsk->comm));
1050         task_unlock(tsk);
1051         return buf;
1052 }
1053 EXPORT_SYMBOL_GPL(get_task_comm);
1054
1055 void set_task_comm(struct task_struct *tsk, char *buf)
1056 {
1057         task_lock(tsk);
1058
1059         /*
1060          * Threads may access current->comm without holding
1061          * the task lock, so write the string carefully.
1062          * Readers without a lock may see incomplete new
1063          * names but are safe from non-terminating string reads.
1064          */
1065         memset(tsk->comm, 0, TASK_COMM_LEN);
1066         wmb();
1067         strlcpy(tsk->comm, buf, sizeof(tsk->comm));
1068         task_unlock(tsk);
1069         perf_event_comm(tsk);
1070 }
1071
1072 int flush_old_exec(struct linux_binprm * bprm)
1073 {
1074         int retval;
1075
1076         /*
1077          * Make sure we have a private signal table and that
1078          * we are unassociated from the previous thread group.
1079          */
1080         retval = de_thread(current);
1081         if (retval)
1082                 goto out;
1083
1084         set_mm_exe_file(bprm->mm, bprm->file);
1085
1086         /*
1087          * Release all of the old mmap stuff
1088          */
1089         acct_arg_size(bprm, 0);
1090         retval = exec_mmap(bprm->mm);
1091         if (retval)
1092                 goto out;
1093
1094         bprm->mm = NULL;                /* We're using it now */
1095
1096         current->flags &= ~(PF_RANDOMIZE | PF_KTHREAD);
1097         flush_thread();
1098         current->personality &= ~bprm->per_clear;
1099
1100         return 0;
1101
1102 out:
1103         return retval;
1104 }
1105 EXPORT_SYMBOL(flush_old_exec);
1106
1107 void setup_new_exec(struct linux_binprm * bprm)
1108 {
1109         int i, ch;
1110         const char *name;
1111         char tcomm[sizeof(current->comm)];
1112
1113         arch_pick_mmap_layout(current->mm);
1114
1115         /* This is the point of no return */
1116         current->sas_ss_sp = current->sas_ss_size = 0;
1117
1118         if (current_euid() == current_uid() && current_egid() == current_gid())
1119                 set_dumpable(current->mm, 1);
1120         else
1121                 set_dumpable(current->mm, suid_dumpable);
1122
1123         name = bprm->filename;
1124
1125         /* Copies the binary name from after last slash */
1126         for (i=0; (ch = *(name++)) != '\0';) {
1127                 if (ch == '/')
1128                         i = 0; /* overwrite what we wrote */
1129                 else
1130                         if (i < (sizeof(tcomm) - 1))
1131                                 tcomm[i++] = ch;
1132         }
1133         tcomm[i] = '\0';
1134         set_task_comm(current, tcomm);
1135
1136         /* Set the new mm task size. We have to do that late because it may
1137          * depend on TIF_32BIT which is only updated in flush_thread() on
1138          * some architectures like powerpc
1139          */
1140         current->mm->task_size = TASK_SIZE;
1141
1142         /* install the new credentials */
1143         if (bprm->cred->uid != current_euid() ||
1144             bprm->cred->gid != current_egid()) {
1145                 current->pdeath_signal = 0;
1146         } else if (file_permission(bprm->file, MAY_READ) ||
1147                    bprm->interp_flags & BINPRM_FLAGS_ENFORCE_NONDUMP) {
1148                 set_dumpable(current->mm, suid_dumpable);
1149         }
1150
1151         /*
1152          * Flush performance counters when crossing a
1153          * security domain:
1154          */
1155         if (!get_dumpable(current->mm))
1156                 perf_event_exit_task(current);
1157
1158         /* An exec changes our domain. We are no longer part of the thread
1159            group */
1160
1161         current->self_exec_id++;
1162
1163         flush_signal_handlers(current, 0);
1164         flush_old_files(current->files);
1165 }
1166 EXPORT_SYMBOL(setup_new_exec);
1167
1168 /*
1169  * Prepare credentials and lock ->cred_guard_mutex.
1170  * install_exec_creds() commits the new creds and drops the lock.
1171  * Or, if exec fails before, free_bprm() should release ->cred and
1172  * and unlock.
1173  */
1174 int prepare_bprm_creds(struct linux_binprm *bprm)
1175 {
1176         if (mutex_lock_interruptible(&current->signal->cred_guard_mutex))
1177                 return -ERESTARTNOINTR;
1178
1179         bprm->cred = prepare_exec_creds();
1180         if (likely(bprm->cred))
1181                 return 0;
1182
1183         mutex_unlock(&current->signal->cred_guard_mutex);
1184         return -ENOMEM;
1185 }
1186
1187 void free_bprm(struct linux_binprm *bprm)
1188 {
1189         free_arg_pages(bprm);
1190         if (bprm->cred) {
1191                 mutex_unlock(&current->signal->cred_guard_mutex);
1192                 abort_creds(bprm->cred);
1193         }
1194         kfree(bprm);
1195 }
1196
1197 /*
1198  * install the new credentials for this executable
1199  */
1200 void install_exec_creds(struct linux_binprm *bprm)
1201 {
1202         security_bprm_committing_creds(bprm);
1203
1204         commit_creds(bprm->cred);
1205         bprm->cred = NULL;
1206         /*
1207          * cred_guard_mutex must be held at least to this point to prevent
1208          * ptrace_attach() from altering our determination of the task's
1209          * credentials; any time after this it may be unlocked.
1210          */
1211         security_bprm_committed_creds(bprm);
1212         mutex_unlock(&current->signal->cred_guard_mutex);
1213 }
1214 EXPORT_SYMBOL(install_exec_creds);
1215
1216 /*
1217  * determine how safe it is to execute the proposed program
1218  * - the caller must hold ->cred_guard_mutex to protect against
1219  *   PTRACE_ATTACH
1220  */
1221 int check_unsafe_exec(struct linux_binprm *bprm)
1222 {
1223         struct task_struct *p = current, *t;
1224         unsigned n_fs;
1225         int res = 0;
1226
1227         bprm->unsafe = tracehook_unsafe_exec(p);
1228
1229         n_fs = 1;
1230         spin_lock(&p->fs->lock);
1231         rcu_read_lock();
1232         for (t = next_thread(p); t != p; t = next_thread(t)) {
1233                 if (t->fs == p->fs)
1234                         n_fs++;
1235         }
1236         rcu_read_unlock();
1237
1238         if (p->fs->users > n_fs) {
1239                 bprm->unsafe |= LSM_UNSAFE_SHARE;
1240         } else {
1241                 res = -EAGAIN;
1242                 if (!p->fs->in_exec) {
1243                         p->fs->in_exec = 1;
1244                         res = 1;
1245                 }
1246         }
1247         spin_unlock(&p->fs->lock);
1248
1249         return res;
1250 }
1251
1252 /*
1253  * Fill the binprm structure from the inode.
1254  * Check permissions, then read the first 128 (BINPRM_BUF_SIZE) bytes
1255  *
1256  * This may be called multiple times for binary chains (scripts for example).
1257  */
1258 int prepare_binprm(struct linux_binprm *bprm)
1259 {
1260         umode_t mode;
1261         struct inode * inode = bprm->file->f_path.dentry->d_inode;
1262         int retval;
1263
1264         mode = inode->i_mode;
1265         if (bprm->file->f_op == NULL)
1266                 return -EACCES;
1267
1268         /* clear any previous set[ug]id data from a previous binary */
1269         bprm->cred->euid = current_euid();
1270         bprm->cred->egid = current_egid();
1271
1272         if (!(bprm->file->f_path.mnt->mnt_flags & MNT_NOSUID)) {
1273                 /* Set-uid? */
1274                 if (mode & S_ISUID) {
1275                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1276                         bprm->cred->euid = inode->i_uid;
1277                 }
1278
1279                 /* Set-gid? */
1280                 /*
1281                  * If setgid is set but no group execute bit then this
1282                  * is a candidate for mandatory locking, not a setgid
1283                  * executable.
1284                  */
1285                 if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP)) {
1286                         bprm->per_clear |= PER_CLEAR_ON_SETID;
1287                         bprm->cred->egid = inode->i_gid;
1288                 }
1289         }
1290
1291         /* fill in binprm security blob */
1292         retval = security_bprm_set_creds(bprm);
1293         if (retval)
1294                 return retval;
1295         bprm->cred_prepared = 1;
1296
1297         memset(bprm->buf, 0, BINPRM_BUF_SIZE);
1298         return kernel_read(bprm->file, 0, bprm->buf, BINPRM_BUF_SIZE);
1299 }
1300
1301 EXPORT_SYMBOL(prepare_binprm);
1302
1303 /*
1304  * Arguments are '\0' separated strings found at the location bprm->p
1305  * points to; chop off the first by relocating brpm->p to right after
1306  * the first '\0' encountered.
1307  */
1308 int remove_arg_zero(struct linux_binprm *bprm)
1309 {
1310         int ret = 0;
1311         unsigned long offset;
1312         char *kaddr;
1313         struct page *page;
1314
1315         if (!bprm->argc)
1316                 return 0;
1317
1318         do {
1319                 offset = bprm->p & ~PAGE_MASK;
1320                 page = get_arg_page(bprm, bprm->p, 0);
1321                 if (!page) {
1322                         ret = -EFAULT;
1323                         goto out;
1324                 }
1325                 kaddr = kmap_atomic(page, KM_USER0);
1326
1327                 for (; offset < PAGE_SIZE && kaddr[offset];
1328                                 offset++, bprm->p++)
1329                         ;
1330
1331                 kunmap_atomic(kaddr, KM_USER0);
1332                 put_arg_page(page);
1333
1334                 if (offset == PAGE_SIZE)
1335                         free_arg_page(bprm, (bprm->p >> PAGE_SHIFT) - 1);
1336         } while (offset == PAGE_SIZE);
1337
1338         bprm->p++;
1339         bprm->argc--;
1340         ret = 0;
1341
1342 out:
1343         return ret;
1344 }
1345 EXPORT_SYMBOL(remove_arg_zero);
1346
1347 /*
1348  * cycle the list of binary formats handler, until one recognizes the image
1349  */
1350 int search_binary_handler(struct linux_binprm *bprm,struct pt_regs *regs)
1351 {
1352         unsigned int depth = bprm->recursion_depth;
1353         int try,retval;
1354         struct linux_binfmt *fmt;
1355
1356         retval = security_bprm_check(bprm);
1357         if (retval)
1358                 return retval;
1359
1360         /* kernel module loader fixup */
1361         /* so we don't try to load run modprobe in kernel space. */
1362         set_fs(USER_DS);
1363
1364         retval = audit_bprm(bprm);
1365         if (retval)
1366                 return retval;
1367
1368         retval = -ENOENT;
1369         for (try=0; try<2; try++) {
1370                 read_lock(&binfmt_lock);
1371                 list_for_each_entry(fmt, &formats, lh) {
1372                         int (*fn)(struct linux_binprm *, struct pt_regs *) = fmt->load_binary;
1373                         if (!fn)
1374                                 continue;
1375                         if (!try_module_get(fmt->module))
1376                                 continue;
1377                         read_unlock(&binfmt_lock);
1378                         retval = fn(bprm, regs);
1379                         /*
1380                          * Restore the depth counter to its starting value
1381                          * in this call, so we don't have to rely on every
1382                          * load_binary function to restore it on return.
1383                          */
1384                         bprm->recursion_depth = depth;
1385                         if (retval >= 0) {
1386                                 if (depth == 0)
1387                                         tracehook_report_exec(fmt, bprm, regs);
1388                                 put_binfmt(fmt);
1389                                 allow_write_access(bprm->file);
1390                                 if (bprm->file)
1391                                         fput(bprm->file);
1392                                 bprm->file = NULL;
1393                                 current->did_exec = 1;
1394                                 proc_exec_connector(current);
1395                                 return retval;
1396                         }
1397                         read_lock(&binfmt_lock);
1398                         put_binfmt(fmt);
1399                         if (retval != -ENOEXEC || bprm->mm == NULL)
1400                                 break;
1401                         if (!bprm->file) {
1402                                 read_unlock(&binfmt_lock);
1403                                 return retval;
1404                         }
1405                 }
1406                 read_unlock(&binfmt_lock);
1407                 if (retval != -ENOEXEC || bprm->mm == NULL) {
1408                         break;
1409 #ifdef CONFIG_MODULES
1410                 } else {
1411 #define printable(c) (((c)=='\t') || ((c)=='\n') || (0x20<=(c) && (c)<=0x7e))
1412                         if (printable(bprm->buf[0]) &&
1413                             printable(bprm->buf[1]) &&
1414                             printable(bprm->buf[2]) &&
1415                             printable(bprm->buf[3]))
1416                                 break; /* -ENOEXEC */
1417                         request_module("binfmt-%04x", *(unsigned short *)(&bprm->buf[2]));
1418 #endif
1419                 }
1420         }
1421         return retval;
1422 }
1423
1424 EXPORT_SYMBOL(search_binary_handler);
1425
1426 /*
1427  * sys_execve() executes a new program.
1428  */
1429 static int do_execve_common(const char *filename,
1430                                 struct user_arg_ptr argv,
1431                                 struct user_arg_ptr envp,
1432                                 struct pt_regs *regs)
1433 {
1434         struct linux_binprm *bprm;
1435         struct file *file;
1436         struct files_struct *displaced;
1437         bool clear_in_exec;
1438         int retval;
1439
1440         retval = unshare_files(&displaced);
1441         if (retval)
1442                 goto out_ret;
1443
1444         retval = -ENOMEM;
1445         bprm = kzalloc(sizeof(*bprm), GFP_KERNEL);
1446         if (!bprm)
1447                 goto out_files;
1448
1449         retval = prepare_bprm_creds(bprm);
1450         if (retval)
1451                 goto out_free;
1452
1453         retval = check_unsafe_exec(bprm);
1454         if (retval < 0)
1455                 goto out_free;
1456         clear_in_exec = retval;
1457         current->in_execve = 1;
1458
1459         file = open_exec(filename);
1460         retval = PTR_ERR(file);
1461         if (IS_ERR(file))
1462                 goto out_unmark;
1463
1464         sched_exec();
1465
1466         bprm->file = file;
1467         bprm->filename = filename;
1468         bprm->interp = filename;
1469
1470         retval = bprm_mm_init(bprm);
1471         if (retval)
1472                 goto out_file;
1473
1474         bprm->argc = count(argv, MAX_ARG_STRINGS);
1475         if ((retval = bprm->argc) < 0)
1476                 goto out;
1477
1478         bprm->envc = count(envp, MAX_ARG_STRINGS);
1479         if ((retval = bprm->envc) < 0)
1480                 goto out;
1481
1482         retval = prepare_binprm(bprm);
1483         if (retval < 0)
1484                 goto out;
1485
1486         retval = copy_strings_kernel(1, &bprm->filename, bprm);
1487         if (retval < 0)
1488                 goto out;
1489
1490         bprm->exec = bprm->p;
1491         retval = copy_strings(bprm->envc, envp, bprm);
1492         if (retval < 0)
1493                 goto out;
1494
1495         retval = copy_strings(bprm->argc, argv, bprm);
1496         if (retval < 0)
1497                 goto out;
1498
1499         retval = search_binary_handler(bprm,regs);
1500         if (retval < 0)
1501                 goto out;
1502
1503         /* execve succeeded */
1504         current->fs->in_exec = 0;
1505         current->in_execve = 0;
1506         acct_update_integrals(current);
1507         free_bprm(bprm);
1508         if (displaced)
1509                 put_files_struct(displaced);
1510         return retval;
1511
1512 out:
1513         if (bprm->mm) {
1514                 acct_arg_size(bprm, 0);
1515                 mmput(bprm->mm);
1516         }
1517
1518 out_file:
1519         if (bprm->file) {
1520                 allow_write_access(bprm->file);
1521                 fput(bprm->file);
1522         }
1523
1524 out_unmark:
1525         if (clear_in_exec)
1526                 current->fs->in_exec = 0;
1527         current->in_execve = 0;
1528
1529 out_free:
1530         free_bprm(bprm);
1531
1532 out_files:
1533         if (displaced)
1534                 reset_files_struct(displaced);
1535 out_ret:
1536         return retval;
1537 }
1538
1539 int do_execve(const char *filename,
1540         const char __user *const __user *__argv,
1541         const char __user *const __user *__envp,
1542         struct pt_regs *regs)
1543 {
1544         struct user_arg_ptr argv = { .ptr.native = __argv };
1545         struct user_arg_ptr envp = { .ptr.native = __envp };
1546         return do_execve_common(filename, argv, envp, regs);
1547 }
1548
1549 #ifdef CONFIG_COMPAT
1550 int compat_do_execve(char *filename,
1551         compat_uptr_t __user *__argv,
1552         compat_uptr_t __user *__envp,
1553         struct pt_regs *regs)
1554 {
1555         struct user_arg_ptr argv = {
1556                 .is_compat = true,
1557                 .ptr.compat = __argv,
1558         };
1559         struct user_arg_ptr envp = {
1560                 .is_compat = true,
1561                 .ptr.compat = __envp,
1562         };
1563         return do_execve_common(filename, argv, envp, regs);
1564 }
1565 #endif
1566
1567 void set_binfmt(struct linux_binfmt *new)
1568 {
1569         struct mm_struct *mm = current->mm;
1570
1571         if (mm->binfmt)
1572                 module_put(mm->binfmt->module);
1573
1574         mm->binfmt = new;
1575         if (new)
1576                 __module_get(new->module);
1577 }
1578
1579 EXPORT_SYMBOL(set_binfmt);
1580
1581 static int expand_corename(struct core_name *cn)
1582 {
1583         char *old_corename = cn->corename;
1584
1585         cn->size = CORENAME_MAX_SIZE * atomic_inc_return(&call_count);
1586         cn->corename = krealloc(old_corename, cn->size, GFP_KERNEL);
1587
1588         if (!cn->corename) {
1589                 kfree(old_corename);
1590                 return -ENOMEM;
1591         }
1592
1593         return 0;
1594 }
1595
1596 static int cn_printf(struct core_name *cn, const char *fmt, ...)
1597 {
1598         char *cur;
1599         int need;
1600         int ret;
1601         va_list arg;
1602
1603         va_start(arg, fmt);
1604         need = vsnprintf(NULL, 0, fmt, arg);
1605         va_end(arg);
1606
1607         if (likely(need < cn->size - cn->used - 1))
1608                 goto out_printf;
1609
1610         ret = expand_corename(cn);
1611         if (ret)
1612                 goto expand_fail;
1613
1614 out_printf:
1615         cur = cn->corename + cn->used;
1616         va_start(arg, fmt);
1617         vsnprintf(cur, need + 1, fmt, arg);
1618         va_end(arg);
1619         cn->used += need;
1620         return 0;
1621
1622 expand_fail:
1623         return ret;
1624 }
1625
1626 static int cn_print_exe_file(struct core_name *cn)
1627 {
1628         struct file *exe_file;
1629         char *pathbuf, *path, *p;
1630         int ret;
1631
1632         exe_file = get_mm_exe_file(current->mm);
1633         if (!exe_file)
1634                 return cn_printf(cn, "(unknown)");
1635
1636         pathbuf = kmalloc(PATH_MAX, GFP_TEMPORARY);
1637         if (!pathbuf) {
1638                 ret = -ENOMEM;
1639                 goto put_exe_file;
1640         }
1641
1642         path = d_path(&exe_file->f_path, pathbuf, PATH_MAX);
1643         if (IS_ERR(path)) {
1644                 ret = PTR_ERR(path);
1645                 goto free_buf;
1646         }
1647
1648         for (p = path; *p; p++)
1649                 if (*p == '/')
1650                         *p = '!';
1651
1652         ret = cn_printf(cn, "%s", path);
1653
1654 free_buf:
1655         kfree(pathbuf);
1656 put_exe_file:
1657         fput(exe_file);
1658         return ret;
1659 }
1660
1661 /* format_corename will inspect the pattern parameter, and output a
1662  * name into corename, which must have space for at least
1663  * CORENAME_MAX_SIZE bytes plus one byte for the zero terminator.
1664  */
1665 static int format_corename(struct core_name *cn, long signr)
1666 {
1667         const struct cred *cred = current_cred();
1668         const char *pat_ptr = core_pattern;
1669         int ispipe = (*pat_ptr == '|');
1670         int pid_in_pattern = 0;
1671         int err = 0;
1672
1673         cn->size = CORENAME_MAX_SIZE * atomic_read(&call_count);
1674         cn->corename = kmalloc(cn->size, GFP_KERNEL);
1675         cn->used = 0;
1676
1677         if (!cn->corename)
1678                 return -ENOMEM;
1679
1680         /* Repeat as long as we have more pattern to process and more output
1681            space */
1682         while (*pat_ptr) {
1683                 if (*pat_ptr != '%') {
1684                         if (*pat_ptr == 0)
1685                                 goto out;
1686                         err = cn_printf(cn, "%c", *pat_ptr++);
1687                 } else {
1688                         switch (*++pat_ptr) {
1689                         /* single % at the end, drop that */
1690                         case 0:
1691                                 goto out;
1692                         /* Double percent, output one percent */
1693                         case '%':
1694                                 err = cn_printf(cn, "%c", '%');
1695                                 break;
1696                         /* pid */
1697                         case 'p':
1698                                 pid_in_pattern = 1;
1699                                 err = cn_printf(cn, "%d",
1700                                               task_tgid_vnr(current));
1701                                 break;
1702                         /* uid */
1703                         case 'u':
1704                                 err = cn_printf(cn, "%d", cred->uid);
1705                                 break;
1706                         /* gid */
1707                         case 'g':
1708                                 err = cn_printf(cn, "%d", cred->gid);
1709                                 break;
1710                         /* signal that caused the coredump */
1711                         case 's':
1712                                 err = cn_printf(cn, "%ld", signr);
1713                                 break;
1714                         /* UNIX time of coredump */
1715                         case 't': {
1716                                 struct timeval tv;
1717                                 do_gettimeofday(&tv);
1718                                 err = cn_printf(cn, "%lu", tv.tv_sec);
1719                                 break;
1720                         }
1721                         /* hostname */
1722                         case 'h':
1723                                 down_read(&uts_sem);
1724                                 err = cn_printf(cn, "%s",
1725                                               utsname()->nodename);
1726                                 up_read(&uts_sem);
1727                                 break;
1728                         /* executable */
1729                         case 'e':
1730                                 err = cn_printf(cn, "%s", current->comm);
1731                                 break;
1732                         case 'E':
1733                                 err = cn_print_exe_file(cn);
1734                                 break;
1735                         /* core limit size */
1736                         case 'c':
1737                                 err = cn_printf(cn, "%lu",
1738                                               rlimit(RLIMIT_CORE));
1739                                 break;
1740                         default:
1741                                 break;
1742                         }
1743                         ++pat_ptr;
1744                 }
1745
1746                 if (err)
1747                         return err;
1748         }
1749
1750         /* Backward compatibility with core_uses_pid:
1751          *
1752          * If core_pattern does not include a %p (as is the default)
1753          * and core_uses_pid is set, then .%pid will be appended to
1754          * the filename. Do not do this for piped commands. */
1755         if (!ispipe && !pid_in_pattern && core_uses_pid) {
1756                 err = cn_printf(cn, ".%d", task_tgid_vnr(current));
1757                 if (err)
1758                         return err;
1759         }
1760 out:
1761         return ispipe;
1762 }
1763
1764 static int zap_process(struct task_struct *start, int exit_code)
1765 {
1766         struct task_struct *t;
1767         int nr = 0;
1768
1769         start->signal->flags = SIGNAL_GROUP_EXIT;
1770         start->signal->group_exit_code = exit_code;
1771         start->signal->group_stop_count = 0;
1772
1773         t = start;
1774         do {
1775                 task_clear_group_stop_pending(t);
1776                 if (t != current && t->mm) {
1777                         sigaddset(&t->pending.signal, SIGKILL);
1778                         signal_wake_up(t, 1);
1779                         nr++;
1780                 }
1781         } while_each_thread(start, t);
1782
1783         return nr;
1784 }
1785
1786 static inline int zap_threads(struct task_struct *tsk, struct mm_struct *mm,
1787                                 struct core_state *core_state, int exit_code)
1788 {
1789         struct task_struct *g, *p;
1790         unsigned long flags;
1791         int nr = -EAGAIN;
1792
1793         spin_lock_irq(&tsk->sighand->siglock);
1794         if (!signal_group_exit(tsk->signal)) {
1795                 mm->core_state = core_state;
1796                 nr = zap_process(tsk, exit_code);
1797         }
1798         spin_unlock_irq(&tsk->sighand->siglock);
1799         if (unlikely(nr < 0))
1800                 return nr;
1801
1802         if (atomic_read(&mm->mm_users) == nr + 1)
1803                 goto done;
1804         /*
1805          * We should find and kill all tasks which use this mm, and we should
1806          * count them correctly into ->nr_threads. We don't take tasklist
1807          * lock, but this is safe wrt:
1808          *
1809          * fork:
1810          *      None of sub-threads can fork after zap_process(leader). All
1811          *      processes which were created before this point should be
1812          *      visible to zap_threads() because copy_process() adds the new
1813          *      process to the tail of init_task.tasks list, and lock/unlock
1814          *      of ->siglock provides a memory barrier.
1815          *
1816          * do_exit:
1817          *      The caller holds mm->mmap_sem. This means that the task which
1818          *      uses this mm can't pass exit_mm(), so it can't exit or clear
1819          *      its ->mm.
1820          *
1821          * de_thread:
1822          *      It does list_replace_rcu(&leader->tasks, &current->tasks),
1823          *      we must see either old or new leader, this does not matter.
1824          *      However, it can change p->sighand, so lock_task_sighand(p)
1825          *      must be used. Since p->mm != NULL and we hold ->mmap_sem
1826          *      it can't fail.
1827          *
1828          *      Note also that "g" can be the old leader with ->mm == NULL
1829          *      and already unhashed and thus removed from ->thread_group.
1830          *      This is OK, __unhash_process()->list_del_rcu() does not
1831          *      clear the ->next pointer, we will find the new leader via
1832          *      next_thread().
1833          */
1834         rcu_read_lock();
1835         for_each_process(g) {
1836                 if (g == tsk->group_leader)
1837                         continue;
1838                 if (g->flags & PF_KTHREAD)
1839                         continue;
1840                 p = g;
1841                 do {
1842                         if (p->mm) {
1843                                 if (unlikely(p->mm == mm)) {
1844                                         lock_task_sighand(p, &flags);
1845                                         nr += zap_process(p, exit_code);
1846                                         unlock_task_sighand(p, &flags);
1847                                 }
1848                                 break;
1849                         }
1850                 } while_each_thread(g, p);
1851         }
1852         rcu_read_unlock();
1853 done:
1854         atomic_set(&core_state->nr_threads, nr);
1855         return nr;
1856 }
1857
1858 static int coredump_wait(int exit_code, struct core_state *core_state)
1859 {
1860         struct task_struct *tsk = current;
1861         struct mm_struct *mm = tsk->mm;
1862         struct completion *vfork_done;
1863         int core_waiters = -EBUSY;
1864
1865         init_completion(&core_state->startup);
1866         core_state->dumper.task = tsk;
1867         core_state->dumper.next = NULL;
1868
1869         down_write(&mm->mmap_sem);
1870         if (!mm->core_state)
1871                 core_waiters = zap_threads(tsk, mm, core_state, exit_code);
1872         up_write(&mm->mmap_sem);
1873
1874         if (unlikely(core_waiters < 0))
1875                 goto fail;
1876
1877         /*
1878          * Make sure nobody is waiting for us to release the VM,
1879          * otherwise we can deadlock when we wait on each other
1880          */
1881         vfork_done = tsk->vfork_done;
1882         if (vfork_done) {
1883                 tsk->vfork_done = NULL;
1884                 complete(vfork_done);
1885         }
1886
1887         if (core_waiters)
1888                 wait_for_completion(&core_state->startup);
1889 fail:
1890         return core_waiters;
1891 }
1892
1893 static void coredump_finish(struct mm_struct *mm)
1894 {
1895         struct core_thread *curr, *next;
1896         struct task_struct *task;
1897
1898         next = mm->core_state->dumper.next;
1899         while ((curr = next) != NULL) {
1900                 next = curr->next;
1901                 task = curr->task;
1902                 /*
1903                  * see exit_mm(), curr->task must not see
1904                  * ->task == NULL before we read ->next.
1905                  */
1906                 smp_mb();
1907                 curr->task = NULL;
1908                 wake_up_process(task);
1909         }
1910
1911         mm->core_state = NULL;
1912 }
1913
1914 /*
1915  * set_dumpable converts traditional three-value dumpable to two flags and
1916  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
1917  * these bits are not changed atomically.  So get_dumpable can observe the
1918  * intermediate state.  To avoid doing unexpected behavior, get get_dumpable
1919  * return either old dumpable or new one by paying attention to the order of
1920  * modifying the bits.
1921  *
1922  * dumpable |   mm->flags (binary)
1923  * old  new | initial interim  final
1924  * ---------+-----------------------
1925  *  0    1  |   00      01      01
1926  *  0    2  |   00      10(*)   11
1927  *  1    0  |   01      00      00
1928  *  1    2  |   01      11      11
1929  *  2    0  |   11      10(*)   00
1930  *  2    1  |   11      11      01
1931  *
1932  * (*) get_dumpable regards interim value of 10 as 11.
1933  */
1934 void set_dumpable(struct mm_struct *mm, int value)
1935 {
1936         switch (value) {
1937         case 0:
1938                 clear_bit(MMF_DUMPABLE, &mm->flags);
1939                 smp_wmb();
1940                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1941                 break;
1942         case 1:
1943                 set_bit(MMF_DUMPABLE, &mm->flags);
1944                 smp_wmb();
1945                 clear_bit(MMF_DUMP_SECURELY, &mm->flags);
1946                 break;
1947         case 2:
1948                 set_bit(MMF_DUMP_SECURELY, &mm->flags);
1949                 smp_wmb();
1950                 set_bit(MMF_DUMPABLE, &mm->flags);
1951                 break;
1952         }
1953 }
1954
1955 static int __get_dumpable(unsigned long mm_flags)
1956 {
1957         int ret;
1958
1959         ret = mm_flags & MMF_DUMPABLE_MASK;
1960         return (ret >= 2) ? 2 : ret;
1961 }
1962
1963 int get_dumpable(struct mm_struct *mm)
1964 {
1965         return __get_dumpable(mm->flags);
1966 }
1967
1968 static void wait_for_dump_helpers(struct file *file)
1969 {
1970         struct pipe_inode_info *pipe;
1971
1972         pipe = file->f_path.dentry->d_inode->i_pipe;
1973
1974         pipe_lock(pipe);
1975         pipe->readers++;
1976         pipe->writers--;
1977
1978         while ((pipe->readers > 1) && (!signal_pending(current))) {
1979                 wake_up_interruptible_sync(&pipe->wait);
1980                 kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
1981                 pipe_wait(pipe);
1982         }
1983
1984         pipe->readers--;
1985         pipe->writers++;
1986         pipe_unlock(pipe);
1987
1988 }
1989
1990
1991 /*
1992  * umh_pipe_setup
1993  * helper function to customize the process used
1994  * to collect the core in userspace.  Specifically
1995  * it sets up a pipe and installs it as fd 0 (stdin)
1996  * for the process.  Returns 0 on success, or
1997  * PTR_ERR on failure.
1998  * Note that it also sets the core limit to 1.  This
1999  * is a special value that we use to trap recursive
2000  * core dumps
2001  */
2002 static int umh_pipe_setup(struct subprocess_info *info)
2003 {
2004         struct file *rp, *wp;
2005         struct fdtable *fdt;
2006         struct coredump_params *cp = (struct coredump_params *)info->data;
2007         struct files_struct *cf = current->files;
2008
2009         wp = create_write_pipe(0);
2010         if (IS_ERR(wp))
2011                 return PTR_ERR(wp);
2012
2013         rp = create_read_pipe(wp, 0);
2014         if (IS_ERR(rp)) {
2015                 free_write_pipe(wp);
2016                 return PTR_ERR(rp);
2017         }
2018
2019         cp->file = wp;
2020
2021         sys_close(0);
2022         fd_install(0, rp);
2023         spin_lock(&cf->file_lock);
2024         fdt = files_fdtable(cf);
2025         FD_SET(0, fdt->open_fds);
2026         FD_CLR(0, fdt->close_on_exec);
2027         spin_unlock(&cf->file_lock);
2028
2029         /* and disallow core files too */
2030         current->signal->rlim[RLIMIT_CORE] = (struct rlimit){1, 1};
2031
2032         return 0;
2033 }
2034
2035 void do_coredump(long signr, int exit_code, struct pt_regs *regs)
2036 {
2037         struct core_state core_state;
2038         struct core_name cn;
2039         struct mm_struct *mm = current->mm;
2040         struct linux_binfmt * binfmt;
2041         const struct cred *old_cred;
2042         struct cred *cred;
2043         int retval = 0;
2044         int flag = 0;
2045         int ispipe;
2046         static atomic_t core_dump_count = ATOMIC_INIT(0);
2047         struct coredump_params cprm = {
2048                 .signr = signr,
2049                 .regs = regs,
2050                 .limit = rlimit(RLIMIT_CORE),
2051                 /*
2052                  * We must use the same mm->flags while dumping core to avoid
2053                  * inconsistency of bit flags, since this flag is not protected
2054                  * by any locks.
2055                  */
2056                 .mm_flags = mm->flags,
2057         };
2058
2059         audit_core_dumps(signr);
2060
2061         binfmt = mm->binfmt;
2062         if (!binfmt || !binfmt->core_dump)
2063                 goto fail;
2064         if (!__get_dumpable(cprm.mm_flags))
2065                 goto fail;
2066
2067         cred = prepare_creds();
2068         if (!cred)
2069                 goto fail;
2070         /*
2071          *      We cannot trust fsuid as being the "true" uid of the
2072          *      process nor do we know its entire history. We only know it
2073          *      was tainted so we dump it as root in mode 2.
2074          */
2075         if (__get_dumpable(cprm.mm_flags) == 2) {
2076                 /* Setuid core dump mode */
2077                 flag = O_EXCL;          /* Stop rewrite attacks */
2078                 cred->fsuid = 0;        /* Dump root private */
2079         }
2080
2081         retval = coredump_wait(exit_code, &core_state);
2082         if (retval < 0)
2083                 goto fail_creds;
2084
2085         old_cred = override_creds(cred);
2086
2087         /*
2088          * Clear any false indication of pending signals that might
2089          * be seen by the filesystem code called to write the core file.
2090          */
2091         clear_thread_flag(TIF_SIGPENDING);
2092
2093         ispipe = format_corename(&cn, signr);
2094
2095         if (ispipe == -ENOMEM) {
2096                 printk(KERN_WARNING "format_corename failed\n");
2097                 printk(KERN_WARNING "Aborting core\n");
2098                 goto fail_corename;
2099         }
2100
2101         if (ispipe) {
2102                 int dump_count;
2103                 char **helper_argv;
2104
2105                 if (cprm.limit == 1) {
2106                         /*
2107                          * Normally core limits are irrelevant to pipes, since
2108                          * we're not writing to the file system, but we use
2109                          * cprm.limit of 1 here as a speacial value. Any
2110                          * non-1 limit gets set to RLIM_INFINITY below, but
2111                          * a limit of 0 skips the dump.  This is a consistent
2112                          * way to catch recursive crashes.  We can still crash
2113                          * if the core_pattern binary sets RLIM_CORE =  !1
2114                          * but it runs as root, and can do lots of stupid things
2115                          * Note that we use task_tgid_vnr here to grab the pid
2116                          * of the process group leader.  That way we get the
2117                          * right pid if a thread in a multi-threaded
2118                          * core_pattern process dies.
2119                          */
2120                         printk(KERN_WARNING
2121                                 "Process %d(%s) has RLIMIT_CORE set to 1\n",
2122                                 task_tgid_vnr(current), current->comm);
2123                         printk(KERN_WARNING "Aborting core\n");
2124                         goto fail_unlock;
2125                 }
2126                 cprm.limit = RLIM_INFINITY;
2127
2128                 dump_count = atomic_inc_return(&core_dump_count);
2129                 if (core_pipe_limit && (core_pipe_limit < dump_count)) {
2130                         printk(KERN_WARNING "Pid %d(%s) over core_pipe_limit\n",
2131                                task_tgid_vnr(current), current->comm);
2132                         printk(KERN_WARNING "Skipping core dump\n");
2133                         goto fail_dropcount;
2134                 }
2135
2136                 helper_argv = argv_split(GFP_KERNEL, cn.corename+1, NULL);
2137                 if (!helper_argv) {
2138                         printk(KERN_WARNING "%s failed to allocate memory\n",
2139                                __func__);
2140                         goto fail_dropcount;
2141                 }
2142
2143                 retval = call_usermodehelper_fns(helper_argv[0], helper_argv,
2144                                         NULL, UMH_WAIT_EXEC, umh_pipe_setup,
2145                                         NULL, &cprm);
2146                 argv_free(helper_argv);
2147                 if (retval) {
2148                         printk(KERN_INFO "Core dump to %s pipe failed\n",
2149                                cn.corename);
2150                         goto close_fail;
2151                 }
2152         } else {
2153                 struct inode *inode;
2154
2155                 if (cprm.limit < binfmt->min_coredump)
2156                         goto fail_unlock;
2157
2158                 cprm.file = filp_open(cn.corename,
2159                                  O_CREAT | 2 | O_NOFOLLOW | O_LARGEFILE | flag,
2160                                  0600);
2161                 if (IS_ERR(cprm.file))
2162                         goto fail_unlock;
2163
2164                 inode = cprm.file->f_path.dentry->d_inode;
2165                 if (inode->i_nlink > 1)
2166                         goto close_fail;
2167                 if (d_unhashed(cprm.file->f_path.dentry))
2168                         goto close_fail;
2169                 /*
2170                  * AK: actually i see no reason to not allow this for named
2171                  * pipes etc, but keep the previous behaviour for now.
2172                  */
2173                 if (!S_ISREG(inode->i_mode))
2174                         goto close_fail;
2175                 /*
2176                  * Dont allow local users get cute and trick others to coredump
2177                  * into their pre-created files.
2178                  */
2179                 if (inode->i_uid != current_fsuid())
2180                         goto close_fail;
2181                 if (!cprm.file->f_op || !cprm.file->f_op->write)
2182                         goto close_fail;
2183                 if (do_truncate(cprm.file->f_path.dentry, 0, 0, cprm.file))
2184                         goto close_fail;
2185         }
2186
2187         retval = binfmt->core_dump(&cprm);
2188         if (retval)
2189                 current->signal->group_exit_code |= 0x80;
2190
2191         if (ispipe && core_pipe_limit)
2192                 wait_for_dump_helpers(cprm.file);
2193 close_fail:
2194         if (cprm.file)
2195                 filp_close(cprm.file, NULL);
2196 fail_dropcount:
2197         if (ispipe)
2198                 atomic_dec(&core_dump_count);
2199 fail_unlock:
2200         kfree(cn.corename);
2201 fail_corename:
2202         coredump_finish(mm);
2203         revert_creds(old_cred);
2204 fail_creds:
2205         put_cred(cred);
2206 fail:
2207         return;
2208 }
2209
2210 /*
2211  * Core dumping helper functions.  These are the only things you should
2212  * do on a core-file: use only these functions to write out all the
2213  * necessary info.
2214  */
2215 int dump_write(struct file *file, const void *addr, int nr)
2216 {
2217         return access_ok(VERIFY_READ, addr, nr) && file->f_op->write(file, addr, nr, &file->f_pos) == nr;
2218 }
2219 EXPORT_SYMBOL(dump_write);
2220
2221 int dump_seek(struct file *file, loff_t off)
2222 {
2223         int ret = 1;
2224
2225         if (file->f_op->llseek && file->f_op->llseek != no_llseek) {
2226                 if (file->f_op->llseek(file, off, SEEK_CUR) < 0)
2227                         return 0;
2228         } else {
2229                 char *buf = (char *)get_zeroed_page(GFP_KERNEL);
2230
2231                 if (!buf)
2232                         return 0;
2233                 while (off > 0) {
2234                         unsigned long n = off;
2235
2236                         if (n > PAGE_SIZE)
2237                                 n = PAGE_SIZE;
2238                         if (!dump_write(file, buf, n)) {
2239                                 ret = 0;
2240                                 break;
2241                         }
2242                         off -= n;
2243                 }
2244                 free_page((unsigned long)buf);
2245         }
2246         return ret;
2247 }
2248 EXPORT_SYMBOL(dump_seek);