fs/readdir.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *  linux/fs/readdir.c
   4  *
   5  *  Copyright (C) 1995  Linus Torvalds
   6  */
   7
   8 #include <linux/stddef.h>
   9 #include <linux/kernel.h>
  10 #include <linux/export.h>
  11 #include <linux/time.h>
  12 #include <linux/mm.h>
  13 #include <linux/errno.h>
  14 #include <linux/stat.h>
  15 #include <linux/file.h>
  16 #include <linux/fs.h>
  17 #include <linux/fsnotify.h>
  18 #include <linux/dirent.h>
  19 #include <linux/security.h>
  20 #include <linux/syscalls.h>
  21 #include <linux/unistd.h>
  22 #include <linux/compat.h>
  23 #include <linux/uaccess.h>
  24
  25 #include <asm/unaligned.h>
  26
  27 /*
  28  * Note the "unsafe_put_user() semantics: we goto a
  29  * label for errors.
  30  */
  31 #define unsafe_copy_dirent_name(_dst, _src, _len, label) do {   \
  32         char __user *dst = (_dst);                              \
  33         const char *src = (_src);                               \
  34         size_t len = (_len);                                    \
  35         unsafe_put_user(0, dst+len, label);                     \
  36         unsafe_copy_to_user(dst, src, len, label);              \
  37 } while (0)
  38
  39
  40 int iterate_dir(struct file *file, struct dir_context *ctx)
  41 {
  42         struct inode *inode = file_inode(file);
  43         bool shared = false;
  44         int res = -ENOTDIR;
  45         if (file->f_op->iterate_shared)
  46                 shared = true;
  47         else if (!file->f_op->iterate)
  48                 goto out;
  49
  50         res = security_file_permission(file, MAY_READ);
  51         if (res)
  52                 goto out;
  53
  54         if (shared)
  55                 res = down_read_killable(&inode->i_rwsem);
  56         else
  57                 res = down_write_killable(&inode->i_rwsem);
  58         if (res)
  59                 goto out;
  60
  61         res = -ENOENT;
  62         if (!IS_DEADDIR(inode)) {
  63                 ctx->pos = file->f_pos;
  64                 if (shared)
  65                         res = file->f_op->iterate_shared(file, ctx);
  66                 else
  67                         res = file->f_op->iterate(file, ctx);
  68                 file->f_pos = ctx->pos;
  69                 fsnotify_access(file);
  70                 file_accessed(file);
  71         }
  72         if (shared)
  73                 inode_unlock_shared(inode);
  74         else
  75                 inode_unlock(inode);
  76 out:
  77         return res;
  78 }
  79 EXPORT_SYMBOL(iterate_dir);
  80
  81 /*
  82  * POSIX says that a dirent name cannot contain NULL or a '/'.
  83  *
  84  * It's not 100% clear what we should really do in this case.
  85  * The filesystem is clearly corrupted, but returning a hard
  86  * error means that you now don't see any of the other names
  87  * either, so that isn't a perfect alternative.
  88  *
  89  * And if you return an error, what error do you use? Several
  90  * filesystems seem to have decided on EUCLEAN being the error
  91  * code for EFSCORRUPTED, and that may be the error to use. Or
  92  * just EIO, which is perhaps more obvious to users.
  93  *
  94  * In order to see the other file names in the directory, the
  95  * caller might want to make this a "soft" error: skip the
  96  * entry, and return the error at the end instead.
  97  *
  98  * Note that this should likely do a "memchr(name, 0, len)"
  99  * check too, since that would be filesystem corruption as
 100  * well. However, that case can't actually confuse user space,
 101  * which has to do a strlen() on the name anyway to find the
 102  * filename length, and the above "soft error" worry means
 103  * that it's probably better left alone until we have that
 104  * issue clarified.
 105  */
 106 static int verify_dirent_name(const char *name, int len)
 107 {
 108         if (!len)
 109                 return -EIO;
 110         if (memchr(name, '/', len))
 111                 return -EIO;
 112         return 0;
 113 }
 114
 115 /*
 116  * Traditional linux readdir() handling..
 117  *
 118  * "count=1" is a special case, meaning that the buffer is one
 119  * dirent-structure in size and that the code can't handle more
 120  * anyway. Thus the special "fillonedir()" function for that
 121  * case (the low-level handlers don't need to care about this).
 122  */
 123
 124 #ifdef __ARCH_WANT_OLD_READDIR
 125
 126 struct old_linux_dirent {
 127         unsigned long   d_ino;
 128         unsigned long   d_offset;
 129         unsigned short  d_namlen;
 130         char            d_name[1];
 131 };
 132
 133 struct readdir_callback {
 134         struct dir_context ctx;
 135         struct old_linux_dirent __user * dirent;
 136         int result;
 137 };
 138
 139 static int fillonedir(struct dir_context *ctx, const char *name, int namlen,
 140                       loff_t offset, u64 ino, unsigned int d_type)
 141 {
 142         struct readdir_callback *buf =
 143                 container_of(ctx, struct readdir_callback, ctx);
 144         struct old_linux_dirent __user * dirent;
 145         unsigned long d_ino;
 146
 147         if (buf->result)
 148                 return -EINVAL;
 149         d_ino = ino;
 150         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 151                 buf->result = -EOVERFLOW;
 152                 return -EOVERFLOW;
 153         }
 154         buf->result++;
 155         dirent = buf->dirent;
 156         if (!access_ok(dirent,
 157                         (unsigned long)(dirent->d_name + namlen + 1) -
 158                                 (unsigned long)dirent))
 159                 goto efault;
 160         if (    __put_user(d_ino, &dirent->d_ino) ||
 161                 __put_user(offset, &dirent->d_offset) ||
 162                 __put_user(namlen, &dirent->d_namlen) ||
 163                 __copy_to_user(dirent->d_name, name, namlen) ||
 164                 __put_user(0, dirent->d_name + namlen))
 165                 goto efault;
 166         return 0;
 167 efault:
 168         buf->result = -EFAULT;
 169         return -EFAULT;
 170 }
 171
 172 SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 173                 struct old_linux_dirent __user *, dirent, unsigned int, count)
 174 {
 175         int error;
 176         struct fd f = fdget_pos(fd);
 177         struct readdir_callback buf = {
 178                 .ctx.actor = fillonedir,
 179                 .dirent = dirent
 180         };
 181
 182         if (!f.file)
 183                 return -EBADF;
 184
 185         error = iterate_dir(f.file, &buf.ctx);
 186         if (buf.result)
 187                 error = buf.result;
 188
 189         fdput_pos(f);
 190         return error;
 191 }
 192
 193 #endif /* __ARCH_WANT_OLD_READDIR */
 194
 195 /*
 196  * New, all-improved, singing, dancing, iBCS2-compliant getdents()
 197  * interface.
 198  */
 199 struct linux_dirent {
 200         unsigned long   d_ino;
 201         unsigned long   d_off;
 202         unsigned short  d_reclen;
 203         char            d_name[1];
 204 };
 205
 206 struct getdents_callback {
 207         struct dir_context ctx;
 208         struct linux_dirent __user * current_dir;
 209         struct linux_dirent __user * previous;
 210         int count;
 211         int error;
 212 };
 213
 214 static int filldir(struct dir_context *ctx, const char *name, int namlen,
 215                    loff_t offset, u64 ino, unsigned int d_type)
 216 {
 217         struct linux_dirent __user * dirent;
 218         struct getdents_callback *buf =
 219                 container_of(ctx, struct getdents_callback, ctx);
 220         unsigned long d_ino;
 221         int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,
 222                 sizeof(long));
 223
 224         buf->error = verify_dirent_name(name, namlen);
 225         if (unlikely(buf->error))
 226                 return buf->error;
 227         buf->error = -EINVAL;   /* only used if we fail.. */
 228         if (reclen > buf->count)
 229                 return -EINVAL;
 230         d_ino = ino;
 231         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 232                 buf->error = -EOVERFLOW;
 233                 return -EOVERFLOW;
 234         }
 235         dirent = buf->previous;
 236         if (dirent && signal_pending(current))
 237                 return -EINTR;
 238
 239         /*
 240          * Note! This range-checks 'previous' (which may be NULL).
 241          * The real range was checked in getdents
 242          */
 243         if (!user_access_begin(dirent, sizeof(*dirent)))
 244                 goto efault;
 245         if (dirent)
 246                 unsafe_put_user(offset, &dirent->d_off, efault_end);
 247         dirent = buf->current_dir;
 248         unsafe_put_user(d_ino, &dirent->d_ino, efault_end);
 249         unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
 250         unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);
 251         unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 252         user_access_end();
 253
 254         buf->previous = dirent;
 255         dirent = (void __user *)dirent + reclen;
 256         buf->current_dir = dirent;
 257         buf->count -= reclen;
 258         return 0;
 259 efault_end:
 260         user_access_end();
 261 efault:
 262         buf->error = -EFAULT;
 263         return -EFAULT;
 264 }
 265
 266 SYSCALL_DEFINE3(getdents, unsigned int, fd,
 267                 struct linux_dirent __user *, dirent, unsigned int, count)
 268 {
 269         struct fd f;
 270         struct linux_dirent __user * lastdirent;
 271         struct getdents_callback buf = {
 272                 .ctx.actor = filldir,
 273                 .count = count,
 274                 .current_dir = dirent
 275         };
 276         int error;
 277
 278         if (!access_ok(dirent, count))
 279                 return -EFAULT;
 280
 281         f = fdget_pos(fd);
 282         if (!f.file)
 283                 return -EBADF;
 284
 285         error = iterate_dir(f.file, &buf.ctx);
 286         if (error >= 0)
 287                 error = buf.error;
 288         lastdirent = buf.previous;
 289         if (lastdirent) {
 290                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 291                         error = -EFAULT;
 292                 else
 293                         error = count - buf.count;
 294         }
 295         fdput_pos(f);
 296         return error;
 297 }
 298
 299 struct getdents_callback64 {
 300         struct dir_context ctx;
 301         struct linux_dirent64 __user * current_dir;
 302         struct linux_dirent64 __user * previous;
 303         int count;
 304         int error;
 305 };
 306
 307 static int filldir64(struct dir_context *ctx, const char *name, int namlen,
 308                      loff_t offset, u64 ino, unsigned int d_type)
 309 {
 310         struct linux_dirent64 __user *dirent;
 311         struct getdents_callback64 *buf =
 312                 container_of(ctx, struct getdents_callback64, ctx);
 313         int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,
 314                 sizeof(u64));
 315
 316         buf->error = verify_dirent_name(name, namlen);
 317         if (unlikely(buf->error))
 318                 return buf->error;
 319         buf->error = -EINVAL;   /* only used if we fail.. */
 320         if (reclen > buf->count)
 321                 return -EINVAL;
 322         dirent = buf->previous;
 323         if (dirent && signal_pending(current))
 324                 return -EINTR;
 325
 326         /*
 327          * Note! This range-checks 'previous' (which may be NULL).
 328          * The real range was checked in getdents
 329          */
 330         if (!user_access_begin(dirent, sizeof(*dirent)))
 331                 goto efault;
 332         if (dirent)
 333                 unsafe_put_user(offset, &dirent->d_off, efault_end);
 334         dirent = buf->current_dir;
 335         unsafe_put_user(ino, &dirent->d_ino, efault_end);
 336         unsafe_put_user(reclen, &dirent->d_reclen, efault_end);
 337         unsafe_put_user(d_type, &dirent->d_type, efault_end);
 338         unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);
 339         user_access_end();
 340
 341         buf->previous = dirent;
 342         dirent = (void __user *)dirent + reclen;
 343         buf->current_dir = dirent;
 344         buf->count -= reclen;
 345         return 0;
 346 efault_end:
 347         user_access_end();
 348 efault:
 349         buf->error = -EFAULT;
 350         return -EFAULT;
 351 }
 352
 353 int ksys_getdents64(unsigned int fd, struct linux_dirent64 __user *dirent,
 354                     unsigned int count)
 355 {
 356         struct fd f;
 357         struct linux_dirent64 __user * lastdirent;
 358         struct getdents_callback64 buf = {
 359                 .ctx.actor = filldir64,
 360                 .count = count,
 361                 .current_dir = dirent
 362         };
 363         int error;
 364
 365         if (!access_ok(dirent, count))
 366                 return -EFAULT;
 367
 368         f = fdget_pos(fd);
 369         if (!f.file)
 370                 return -EBADF;
 371
 372         error = iterate_dir(f.file, &buf.ctx);
 373         if (error >= 0)
 374                 error = buf.error;
 375         lastdirent = buf.previous;
 376         if (lastdirent) {
 377                 typeof(lastdirent->d_off) d_off = buf.ctx.pos;
 378                 if (__put_user(d_off, &lastdirent->d_off))
 379                         error = -EFAULT;
 380                 else
 381                         error = count - buf.count;
 382         }
 383         fdput_pos(f);
 384         return error;
 385 }
 386
 387
 388 SYSCALL_DEFINE3(getdents64, unsigned int, fd,
 389                 struct linux_dirent64 __user *, dirent, unsigned int, count)
 390 {
 391         return ksys_getdents64(fd, dirent, count);
 392 }
 393
 394 #ifdef CONFIG_COMPAT
 395 struct compat_old_linux_dirent {
 396         compat_ulong_t  d_ino;
 397         compat_ulong_t  d_offset;
 398         unsigned short  d_namlen;
 399         char            d_name[1];
 400 };
 401
 402 struct compat_readdir_callback {
 403         struct dir_context ctx;
 404         struct compat_old_linux_dirent __user *dirent;
 405         int result;
 406 };
 407
 408 static int compat_fillonedir(struct dir_context *ctx, const char *name,
 409                              int namlen, loff_t offset, u64 ino,
 410                              unsigned int d_type)
 411 {
 412         struct compat_readdir_callback *buf =
 413                 container_of(ctx, struct compat_readdir_callback, ctx);
 414         struct compat_old_linux_dirent __user *dirent;
 415         compat_ulong_t d_ino;
 416
 417         if (buf->result)
 418                 return -EINVAL;
 419         d_ino = ino;
 420         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 421                 buf->result = -EOVERFLOW;
 422                 return -EOVERFLOW;
 423         }
 424         buf->result++;
 425         dirent = buf->dirent;
 426         if (!access_ok(dirent,
 427                         (unsigned long)(dirent->d_name + namlen + 1) -
 428                                 (unsigned long)dirent))
 429                 goto efault;
 430         if (    __put_user(d_ino, &dirent->d_ino) ||
 431                 __put_user(offset, &dirent->d_offset) ||
 432                 __put_user(namlen, &dirent->d_namlen) ||
 433                 __copy_to_user(dirent->d_name, name, namlen) ||
 434                 __put_user(0, dirent->d_name + namlen))
 435                 goto efault;
 436         return 0;
 437 efault:
 438         buf->result = -EFAULT;
 439         return -EFAULT;
 440 }
 441
 442 COMPAT_SYSCALL_DEFINE3(old_readdir, unsigned int, fd,
 443                 struct compat_old_linux_dirent __user *, dirent, unsigned int, count)
 444 {
 445         int error;
 446         struct fd f = fdget_pos(fd);
 447         struct compat_readdir_callback buf = {
 448                 .ctx.actor = compat_fillonedir,
 449                 .dirent = dirent
 450         };
 451
 452         if (!f.file)
 453                 return -EBADF;
 454
 455         error = iterate_dir(f.file, &buf.ctx);
 456         if (buf.result)
 457                 error = buf.result;
 458
 459         fdput_pos(f);
 460         return error;
 461 }
 462
 463 struct compat_linux_dirent {
 464         compat_ulong_t  d_ino;
 465         compat_ulong_t  d_off;
 466         unsigned short  d_reclen;
 467         char            d_name[1];
 468 };
 469
 470 struct compat_getdents_callback {
 471         struct dir_context ctx;
 472         struct compat_linux_dirent __user *current_dir;
 473         struct compat_linux_dirent __user *previous;
 474         int count;
 475         int error;
 476 };
 477
 478 static int compat_filldir(struct dir_context *ctx, const char *name, int namlen,
 479                 loff_t offset, u64 ino, unsigned int d_type)
 480 {
 481         struct compat_linux_dirent __user * dirent;
 482         struct compat_getdents_callback *buf =
 483                 container_of(ctx, struct compat_getdents_callback, ctx);
 484         compat_ulong_t d_ino;
 485         int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +
 486                 namlen + 2, sizeof(compat_long_t));
 487
 488         buf->error = -EINVAL;   /* only used if we fail.. */
 489         if (reclen > buf->count)
 490                 return -EINVAL;
 491         d_ino = ino;
 492         if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {
 493                 buf->error = -EOVERFLOW;
 494                 return -EOVERFLOW;
 495         }
 496         dirent = buf->previous;
 497         if (dirent) {
 498                 if (signal_pending(current))
 499                         return -EINTR;
 500                 if (__put_user(offset, &dirent->d_off))
 501                         goto efault;
 502         }
 503         dirent = buf->current_dir;
 504         if (__put_user(d_ino, &dirent->d_ino))
 505                 goto efault;
 506         if (__put_user(reclen, &dirent->d_reclen))
 507                 goto efault;
 508         if (copy_to_user(dirent->d_name, name, namlen))
 509                 goto efault;
 510         if (__put_user(0, dirent->d_name + namlen))
 511                 goto efault;
 512         if (__put_user(d_type, (char  __user *) dirent + reclen - 1))
 513                 goto efault;
 514         buf->previous = dirent;
 515         dirent = (void __user *)dirent + reclen;
 516         buf->current_dir = dirent;
 517         buf->count -= reclen;
 518         return 0;
 519 efault:
 520         buf->error = -EFAULT;
 521         return -EFAULT;
 522 }
 523
 524 COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,
 525                 struct compat_linux_dirent __user *, dirent, unsigned int, count)
 526 {
 527         struct fd f;
 528         struct compat_linux_dirent __user * lastdirent;
 529         struct compat_getdents_callback buf = {
 530                 .ctx.actor = compat_filldir,
 531                 .current_dir = dirent,
 532                 .count = count
 533         };
 534         int error;
 535
 536         if (!access_ok(dirent, count))
 537                 return -EFAULT;
 538
 539         f = fdget_pos(fd);
 540         if (!f.file)
 541                 return -EBADF;
 542
 543         error = iterate_dir(f.file, &buf.ctx);
 544         if (error >= 0)
 545                 error = buf.error;
 546         lastdirent = buf.previous;
 547         if (lastdirent) {
 548                 if (put_user(buf.ctx.pos, &lastdirent->d_off))
 549                         error = -EFAULT;
 550                 else
 551                         error = count - buf.count;
 552         }
 553         fdput_pos(f);
 554         return error;
 555 }
 556 #endif