fs/cifs/link.c

   1 /*
   2  *   fs/cifs/link.c
   3  *
   4  *   Copyright (C) International Business Machines  Corp., 2002,2008
   5  *   Author(s): Steve French (sfrench@us.ibm.com)
   6  *
   7  *   This library is free software; you can redistribute it and/or modify
   8  *   it under the terms of the GNU Lesser General Public License as published
   9  *   by the Free Software Foundation; either version 2.1 of the License, or
  10  *   (at your option) any later version.
  11  *
  12  *   This library is distributed in the hope that it will be useful,
  13  *   but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
  15  *   the GNU Lesser General Public License for more details.
  16  *
  17  *   You should have received a copy of the GNU Lesser General Public License
  18  *   along with this library; if not, write to the Free Software
  19  *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  20  */
  21 #include <linux/fs.h>
  22 #include <linux/stat.h>
  23 #include <linux/slab.h>
  24 #include <linux/namei.h>
  25 #include "cifsfs.h"
  26 #include "cifspdu.h"
  27 #include "cifsglob.h"
  28 #include "cifsproto.h"
  29 #include "cifs_debug.h"
  30 #include "cifs_fs_sb.h"
  31 #include "md5.h"
  32
  33 #define CIFS_MF_SYMLINK_LEN_OFFSET (4+1)
  34 #define CIFS_MF_SYMLINK_MD5_OFFSET (CIFS_MF_SYMLINK_LEN_OFFSET+(4+1))
  35 #define CIFS_MF_SYMLINK_LINK_OFFSET (CIFS_MF_SYMLINK_MD5_OFFSET+(32+1))
  36 #define CIFS_MF_SYMLINK_LINK_MAXLEN (1024)
  37 #define CIFS_MF_SYMLINK_FILE_SIZE \
  38         (CIFS_MF_SYMLINK_LINK_OFFSET + CIFS_MF_SYMLINK_LINK_MAXLEN)
  39
  40 #define CIFS_MF_SYMLINK_LEN_FORMAT "XSym\n%04u\n"
  41 #define CIFS_MF_SYMLINK_MD5_FORMAT \
  42         "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n"
  43 #define CIFS_MF_SYMLINK_MD5_ARGS(md5_hash) \
  44         md5_hash[0],  md5_hash[1],  md5_hash[2],  md5_hash[3], \
  45         md5_hash[4],  md5_hash[5],  md5_hash[6],  md5_hash[7], \
  46         md5_hash[8],  md5_hash[9],  md5_hash[10], md5_hash[11],\
  47         md5_hash[12], md5_hash[13], md5_hash[14], md5_hash[15]
  48
  49 static int
  50 CIFSParseMFSymlink(const u8 *buf,
  51                    unsigned int buf_len,
  52                    unsigned int *_link_len,
  53                    char **_link_str)
  54 {
  55         int rc;
  56         unsigned int link_len;
  57         const char *md5_str1;
  58         const char *link_str;
  59         struct MD5Context md5_ctx;
  60         u8 md5_hash[16];
  61         char md5_str2[34];
  62
  63         if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
  64                 return -EINVAL;
  65
  66         md5_str1 = (const char *)&buf[CIFS_MF_SYMLINK_MD5_OFFSET];
  67         link_str = (const char *)&buf[CIFS_MF_SYMLINK_LINK_OFFSET];
  68
  69         rc = sscanf(buf, CIFS_MF_SYMLINK_LEN_FORMAT, &link_len);
  70         if (rc != 1)
  71                 return -EINVAL;
  72
  73         cifs_MD5_init(&md5_ctx);
  74         cifs_MD5_update(&md5_ctx, (const u8 *)link_str, link_len);
  75         cifs_MD5_final(md5_hash, &md5_ctx);
  76
  77         snprintf(md5_str2, sizeof(md5_str2),
  78                  CIFS_MF_SYMLINK_MD5_FORMAT,
  79                  CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));
  80
  81         if (strncmp(md5_str1, md5_str2, 17) != 0)
  82                 return -EINVAL;
  83
  84         if (_link_str) {
  85                 *_link_str = kstrndup(link_str, link_len, GFP_KERNEL);
  86                 if (!*_link_str)
  87                         return -ENOMEM;
  88         }
  89
  90         *_link_len = link_len;
  91         return 0;
  92 }
  93
  94 static int
  95 CIFSFormatMFSymlink(u8 *buf, unsigned int buf_len, const char *link_str)
  96 {
  97         unsigned int link_len;
  98         unsigned int ofs;
  99         struct MD5Context md5_ctx;
 100         u8 md5_hash[16];
 101
 102         if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
 103                 return -EINVAL;
 104
 105         link_len = strlen(link_str);
 106
 107         if (link_len > CIFS_MF_SYMLINK_LINK_MAXLEN)
 108                 return -ENAMETOOLONG;
 109
 110         cifs_MD5_init(&md5_ctx);
 111         cifs_MD5_update(&md5_ctx, (const u8 *)link_str, link_len);
 112         cifs_MD5_final(md5_hash, &md5_ctx);
 113
 114         snprintf(buf, buf_len,
 115                  CIFS_MF_SYMLINK_LEN_FORMAT CIFS_MF_SYMLINK_MD5_FORMAT,
 116                  link_len,
 117                  CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));
 118
 119         ofs = CIFS_MF_SYMLINK_LINK_OFFSET;
 120         memcpy(buf + ofs, link_str, link_len);
 121
 122         ofs += link_len;
 123         if (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
 124                 buf[ofs] = '\n';
 125                 ofs++;
 126         }
 127
 128         while (ofs < CIFS_MF_SYMLINK_FILE_SIZE) {
 129                 buf[ofs] = ' ';
 130                 ofs++;
 131         }
 132
 133         return 0;
 134 }
 135
 136 static int
 137 CIFSCreateMFSymLink(const int xid, struct cifsTconInfo *tcon,
 138                     const char *fromName, const char *toName,
 139                     const struct nls_table *nls_codepage, int remap)
 140 {
 141         int rc;
 142         int oplock = 0;
 143         __u16 netfid = 0;
 144         u8 *buf;
 145         unsigned int bytes_written = 0;
 146
 147         buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
 148         if (!buf)
 149                 return -ENOMEM;
 150
 151         rc = CIFSFormatMFSymlink(buf, CIFS_MF_SYMLINK_FILE_SIZE, toName);
 152         if (rc != 0) {
 153                 kfree(buf);
 154                 return rc;
 155         }
 156
 157         rc = CIFSSMBOpen(xid, tcon, fromName, FILE_CREATE, GENERIC_WRITE,
 158                          CREATE_NOT_DIR, &netfid, &oplock, NULL,
 159                          nls_codepage, remap);
 160         if (rc != 0) {
 161                 kfree(buf);
 162                 return rc;
 163         }
 164
 165         rc = CIFSSMBWrite(xid, tcon, netfid,
 166                           CIFS_MF_SYMLINK_FILE_SIZE /* length */,
 167                           0 /* offset */,
 168                           &bytes_written, buf, NULL, 0);
 169         CIFSSMBClose(xid, tcon, netfid);
 170         kfree(buf);
 171         if (rc != 0)
 172                 return rc;
 173
 174         if (bytes_written != CIFS_MF_SYMLINK_FILE_SIZE)
 175                 return -EIO;
 176
 177         return 0;
 178 }
 179
 180 static int
 181 CIFSQueryMFSymLink(const int xid, struct cifsTconInfo *tcon,
 182                    const unsigned char *searchName, char **symlinkinfo,
 183                    const struct nls_table *nls_codepage, int remap)
 184 {
 185         int rc;
 186         int oplock = 0;
 187         __u16 netfid = 0;
 188         u8 *buf;
 189         char *pbuf;
 190         unsigned int bytes_read = 0;
 191         int buf_type = CIFS_NO_BUFFER;
 192         unsigned int link_len = 0;
 193         FILE_ALL_INFO file_info;
 194
 195         rc = CIFSSMBOpen(xid, tcon, searchName, FILE_OPEN, GENERIC_READ,
 196                          CREATE_NOT_DIR, &netfid, &oplock, &file_info,
 197                          nls_codepage, remap);
 198         if (rc != 0)
 199                 return rc;
 200
 201         if (file_info.EndOfFile != CIFS_MF_SYMLINK_FILE_SIZE) {
 202                 CIFSSMBClose(xid, tcon, netfid);
 203                 /* it's not a symlink */
 204                 return -EINVAL;
 205         }
 206
 207         buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
 208         if (!buf)
 209                 return -ENOMEM;
 210         pbuf = buf;
 211
 212         rc = CIFSSMBRead(xid, tcon, netfid,
 213                          CIFS_MF_SYMLINK_FILE_SIZE /* length */,
 214                          0 /* offset */,
 215                          &bytes_read, &pbuf, &buf_type);
 216         CIFSSMBClose(xid, tcon, netfid);
 217         if (rc != 0) {
 218                 kfree(buf);
 219                 return rc;
 220         }
 221
 222         rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, symlinkinfo);
 223         kfree(buf);
 224         if (rc != 0)
 225                 return rc;
 226
 227         return 0;
 228 }
 229
 230 bool
 231 CIFSCouldBeMFSymlink(const struct cifs_fattr *fattr)
 232 {
 233         if (!(fattr->cf_mode & S_IFREG))
 234                 /* it's not a symlink */
 235                 return false;
 236
 237         if (fattr->cf_eof != CIFS_MF_SYMLINK_FILE_SIZE)
 238                 /* it's not a symlink */
 239                 return false;
 240
 241         return true;
 242 }
 243
 244 int
 245 CIFSCheckMFSymlink(struct cifs_fattr *fattr,
 246                    const unsigned char *path,
 247                    struct cifs_sb_info *cifs_sb, int xid)
 248 {
 249         int rc;
 250         int oplock = 0;
 251         __u16 netfid = 0;
 252         struct tcon_link *tlink;
 253         struct cifsTconInfo *pTcon;
 254         u8 *buf;
 255         char *pbuf;
 256         unsigned int bytes_read = 0;
 257         int buf_type = CIFS_NO_BUFFER;
 258         unsigned int link_len = 0;
 259         FILE_ALL_INFO file_info;
 260
 261         if (!CIFSCouldBeMFSymlink(fattr))
 262                 /* it's not a symlink */
 263                 return 0;
 264
 265         tlink = cifs_sb_tlink(cifs_sb);
 266         if (IS_ERR(tlink))
 267                 return PTR_ERR(tlink);
 268         pTcon = tlink_tcon(tlink);
 269
 270         rc = CIFSSMBOpen(xid, pTcon, path, FILE_OPEN, GENERIC_READ,
 271                          CREATE_NOT_DIR, &netfid, &oplock, &file_info,
 272                          cifs_sb->local_nls,
 273                          cifs_sb->mnt_cifs_flags &
 274                                 CIFS_MOUNT_MAP_SPECIAL_CHR);
 275         if (rc != 0)
 276                 goto out;
 277
 278         if (file_info.EndOfFile != CIFS_MF_SYMLINK_FILE_SIZE) {
 279                 CIFSSMBClose(xid, pTcon, netfid);
 280                 /* it's not a symlink */
 281                 goto out;
 282         }
 283
 284         buf = kmalloc(CIFS_MF_SYMLINK_FILE_SIZE, GFP_KERNEL);
 285         if (!buf) {
 286                 rc = -ENOMEM;
 287                 goto out;
 288         }
 289         pbuf = buf;
 290
 291         rc = CIFSSMBRead(xid, pTcon, netfid,
 292                          CIFS_MF_SYMLINK_FILE_SIZE /* length */,
 293                          0 /* offset */,
 294                          &bytes_read, &pbuf, &buf_type);
 295         CIFSSMBClose(xid, pTcon, netfid);
 296         if (rc != 0) {
 297                 kfree(buf);
 298                 goto out;
 299         }
 300
 301         rc = CIFSParseMFSymlink(buf, bytes_read, &link_len, NULL);
 302         kfree(buf);
 303         if (rc == -EINVAL) {
 304                 /* it's not a symlink */
 305                 rc = 0;
 306                 goto out;
 307         }
 308
 309         if (rc != 0)
 310                 goto out;
 311
 312         /* it is a symlink */
 313         fattr->cf_eof = link_len;
 314         fattr->cf_mode &= ~S_IFMT;
 315         fattr->cf_mode |= S_IFLNK | S_IRWXU | S_IRWXG | S_IRWXO;
 316         fattr->cf_dtype = DT_LNK;
 317 out:
 318         cifs_put_tlink(tlink);
 319         return rc;
 320 }
 321
 322 int
 323 cifs_hardlink(struct dentry *old_file, struct inode *inode,
 324               struct dentry *direntry)
 325 {
 326         int rc = -EACCES;
 327         int xid;
 328         char *fromName = NULL;
 329         char *toName = NULL;
 330         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 331         struct tcon_link *tlink;
 332         struct cifsTconInfo *pTcon;
 333         struct cifsInodeInfo *cifsInode;
 334
 335         tlink = cifs_sb_tlink(cifs_sb);
 336         if (IS_ERR(tlink))
 337                 return PTR_ERR(tlink);
 338         pTcon = tlink_tcon(tlink);
 339
 340         xid = GetXid();
 341
 342         fromName = build_path_from_dentry(old_file);
 343         toName = build_path_from_dentry(direntry);
 344         if ((fromName == NULL) || (toName == NULL)) {
 345                 rc = -ENOMEM;
 346                 goto cifs_hl_exit;
 347         }
 348
 349         if (pTcon->unix_ext)
 350                 rc = CIFSUnixCreateHardLink(xid, pTcon, fromName, toName,
 351                                             cifs_sb->local_nls,
 352                                             cifs_sb->mnt_cifs_flags &
 353                                                 CIFS_MOUNT_MAP_SPECIAL_CHR);
 354         else {
 355                 rc = CIFSCreateHardLink(xid, pTcon, fromName, toName,
 356                                         cifs_sb->local_nls,
 357                                         cifs_sb->mnt_cifs_flags &
 358                                                 CIFS_MOUNT_MAP_SPECIAL_CHR);
 359                 if ((rc == -EIO) || (rc == -EINVAL))
 360                         rc = -EOPNOTSUPP;
 361         }
 362
 363         d_drop(direntry);       /* force new lookup from server of target */
 364
 365         /* if source file is cached (oplocked) revalidate will not go to server
 366            until the file is closed or oplock broken so update nlinks locally */
 367         if (old_file->d_inode) {
 368                 cifsInode = CIFS_I(old_file->d_inode);
 369                 if (rc == 0) {
 370                         old_file->d_inode->i_nlink++;
 371 /* BB should we make this contingent on superblock flag NOATIME? */
 372 /*                      old_file->d_inode->i_ctime = CURRENT_TIME;*/
 373                         /* parent dir timestamps will update from srv
 374                         within a second, would it really be worth it
 375                         to set the parent dir cifs inode time to zero
 376                         to force revalidate (faster) for it too? */
 377                 }
 378                 /* if not oplocked will force revalidate to get info
 379                    on source file from srv */
 380                 cifsInode->time = 0;
 381
 382                 /* Will update parent dir timestamps from srv within a second.
 383                    Would it really be worth it to set the parent dir (cifs
 384                    inode) time field to zero to force revalidate on parent
 385                    directory faster ie
 386                         CIFS_I(inode)->time = 0;  */
 387         }
 388
 389 cifs_hl_exit:
 390         kfree(fromName);
 391         kfree(toName);
 392         FreeXid(xid);
 393         cifs_put_tlink(tlink);
 394         return rc;
 395 }
 396
 397 void *
 398 cifs_follow_link(struct dentry *direntry, struct nameidata *nd)
 399 {
 400         struct inode *inode = direntry->d_inode;
 401         int rc = -ENOMEM;
 402         int xid;
 403         char *full_path = NULL;
 404         char *target_path = NULL;
 405         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 406         struct tcon_link *tlink = NULL;
 407         struct cifsTconInfo *tcon;
 408
 409         xid = GetXid();
 410
 411         tlink = cifs_sb_tlink(cifs_sb);
 412         if (IS_ERR(tlink)) {
 413                 rc = PTR_ERR(tlink);
 414                 tlink = NULL;
 415                 goto out;
 416         }
 417         tcon = tlink_tcon(tlink);
 418
 419         /*
 420          * For now, we just handle symlinks with unix extensions enabled.
 421          * Eventually we should handle NTFS reparse points, and MacOS
 422          * symlink support. For instance...
 423          *
 424          * rc = CIFSSMBQueryReparseLinkInfo(...)
 425          *
 426          * For now, just return -EACCES when the server doesn't support posix
 427          * extensions. Note that we still allow querying symlinks when posix
 428          * extensions are manually disabled. We could disable these as well
 429          * but there doesn't seem to be any harm in allowing the client to
 430          * read them.
 431          */
 432         if (!(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
 433             && !(tcon->ses->capabilities & CAP_UNIX)) {
 434                 rc = -EACCES;
 435                 goto out;
 436         }
 437
 438         full_path = build_path_from_dentry(direntry);
 439         if (!full_path)
 440                 goto out;
 441
 442         cFYI(1, "Full path: %s inode = 0x%p", full_path, inode);
 443
 444         rc = -EACCES;
 445         /*
 446          * First try Minshall+French Symlinks, if configured
 447          * and fallback to UNIX Extensions Symlinks.
 448          */
 449         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
 450                 rc = CIFSQueryMFSymLink(xid, tcon, full_path, &target_path,
 451                                         cifs_sb->local_nls,
 452                                         cifs_sb->mnt_cifs_flags &
 453                                                 CIFS_MOUNT_MAP_SPECIAL_CHR);
 454
 455         if ((rc != 0) && (tcon->ses->capabilities & CAP_UNIX))
 456                 rc = CIFSSMBUnixQuerySymLink(xid, tcon, full_path, &target_path,
 457                                              cifs_sb->local_nls);
 458
 459         kfree(full_path);
 460 out:
 461         if (rc != 0) {
 462                 kfree(target_path);
 463                 target_path = ERR_PTR(rc);
 464         }
 465
 466         FreeXid(xid);
 467         if (tlink)
 468                 cifs_put_tlink(tlink);
 469         nd_set_link(nd, target_path);
 470         return NULL;
 471 }
 472
 473 int
 474 cifs_symlink(struct inode *inode, struct dentry *direntry, const char *symname)
 475 {
 476         int rc = -EOPNOTSUPP;
 477         int xid;
 478         struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
 479         struct tcon_link *tlink;
 480         struct cifsTconInfo *pTcon;
 481         char *full_path = NULL;
 482         struct inode *newinode = NULL;
 483
 484         xid = GetXid();
 485
 486         tlink = cifs_sb_tlink(cifs_sb);
 487         if (IS_ERR(tlink)) {
 488                 rc = PTR_ERR(tlink);
 489                 goto symlink_exit;
 490         }
 491         pTcon = tlink_tcon(tlink);
 492
 493         full_path = build_path_from_dentry(direntry);
 494         if (full_path == NULL) {
 495                 rc = -ENOMEM;
 496                 goto symlink_exit;
 497         }
 498
 499         cFYI(1, "Full path: %s", full_path);
 500         cFYI(1, "symname is %s", symname);
 501
 502         /* BB what if DFS and this volume is on different share? BB */
 503         if (cifs_sb->mnt_cifs_flags & CIFS_MOUNT_MF_SYMLINKS)
 504                 rc = CIFSCreateMFSymLink(xid, pTcon, full_path, symname,
 505                                          cifs_sb->local_nls,
 506                                          cifs_sb->mnt_cifs_flags &
 507                                                 CIFS_MOUNT_MAP_SPECIAL_CHR);
 508         else if (pTcon->unix_ext)
 509                 rc = CIFSUnixCreateSymLink(xid, pTcon, full_path, symname,
 510                                            cifs_sb->local_nls);
 511         /* else
 512            rc = CIFSCreateReparseSymLink(xid, pTcon, fromName, toName,
 513                                         cifs_sb_target->local_nls); */
 514
 515         if (rc == 0) {
 516                 if (pTcon->unix_ext)
 517                         rc = cifs_get_inode_info_unix(&newinode, full_path,
 518                                                       inode->i_sb, xid);
 519                 else
 520                         rc = cifs_get_inode_info(&newinode, full_path, NULL,
 521                                                  inode->i_sb, xid, NULL);
 522
 523                 if (rc != 0) {
 524                         cFYI(1, "Create symlink ok, getinodeinfo fail rc = %d",
 525                               rc);
 526                 } else {
 527                         d_instantiate(direntry, newinode);
 528                 }
 529         }
 530 symlink_exit:
 531         kfree(full_path);
 532         cifs_put_tlink(tlink);
 533         FreeXid(xid);
 534         return rc;
 535 }
 536
 537 void cifs_put_link(struct dentry *direntry, struct nameidata *nd, void *cookie)
 538 {
 539         char *p = nd_get_link(nd);
 540         if (!IS_ERR(p))
 541                 kfree(p);
 542 }