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