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