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