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1// SPDX-License-Identifier: GPL-2.02/*3 * linux/fs/readdir.c4 *5 * Copyright (C) 1995 Linus Torvalds6 */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/*26 * Some filesystems were never converted to '->iterate_shared()'27 * and their directory iterators want the inode lock held for28 * writing. This wrapper allows for converting from the shared29 * semantics to the exclusive inode use.30 */31int wrap_directory_iterator(struct file *file,32 struct dir_context *ctx,33 int (*iter)(struct file *, struct dir_context *))34{35 struct inode *inode = file_inode(file);36 int ret;37 38 /*39 * We'd love to have an 'inode_upgrade_trylock()' operation,40 * see the comment in mmap_upgrade_trylock() in mm/memory.c.41 *42 * But considering this is for "filesystems that never got43 * converted", it really doesn't matter.44 *45 * Also note that since we have to return with the lock held46 * for reading, we can't use the "killable()" locking here,47 * since we do need to get the lock even if we're dying.48 *49 * We could do the write part killably and then get the read50 * lock unconditionally if it mattered, but see above on why51 * this does the very simplistic conversion.52 */53 up_read(&inode->i_rwsem);54 down_write(&inode->i_rwsem);55 56 /*57 * Since we dropped the inode lock, we should do the58 * DEADDIR test again. See 'iterate_dir()' below.59 *60 * Note that we don't need to re-do the f_pos games,61 * since the file must be locked wrt f_pos anyway.62 */63 ret = -ENOENT;64 if (!IS_DEADDIR(inode))65 ret = iter(file, ctx);66 67 downgrade_write(&inode->i_rwsem);68 return ret;69}70EXPORT_SYMBOL(wrap_directory_iterator);71 72/*73 * Note the "unsafe_put_user()" semantics: we goto a74 * label for errors.75 */76#define unsafe_copy_dirent_name(_dst, _src, _len, label) do { \77 char __user *dst = (_dst); \78 const char *src = (_src); \79 size_t len = (_len); \80 unsafe_put_user(0, dst+len, label); \81 unsafe_copy_to_user(dst, src, len, label); \82} while (0)83 84 85int iterate_dir(struct file *file, struct dir_context *ctx)86{87 struct inode *inode = file_inode(file);88 int res = -ENOTDIR;89 90 if (!file->f_op->iterate_shared)91 goto out;92 93 res = security_file_permission(file, MAY_READ);94 if (res)95 goto out;96 97 res = fsnotify_file_perm(file, MAY_READ);98 if (res)99 goto out;100 101 res = down_read_killable(&inode->i_rwsem);102 if (res)103 goto out;104 105 res = -ENOENT;106 if (!IS_DEADDIR(inode)) {107 ctx->pos = file->f_pos;108 res = file->f_op->iterate_shared(file, ctx);109 file->f_pos = ctx->pos;110 fsnotify_access(file);111 file_accessed(file);112 }113 inode_unlock_shared(inode);114out:115 return res;116}117EXPORT_SYMBOL(iterate_dir);118 119/*120 * POSIX says that a dirent name cannot contain NULL or a '/'.121 *122 * It's not 100% clear what we should really do in this case.123 * The filesystem is clearly corrupted, but returning a hard124 * error means that you now don't see any of the other names125 * either, so that isn't a perfect alternative.126 *127 * And if you return an error, what error do you use? Several128 * filesystems seem to have decided on EUCLEAN being the error129 * code for EFSCORRUPTED, and that may be the error to use. Or130 * just EIO, which is perhaps more obvious to users.131 *132 * In order to see the other file names in the directory, the133 * caller might want to make this a "soft" error: skip the134 * entry, and return the error at the end instead.135 *136 * Note that this should likely do a "memchr(name, 0, len)"137 * check too, since that would be filesystem corruption as138 * well. However, that case can't actually confuse user space,139 * which has to do a strlen() on the name anyway to find the140 * filename length, and the above "soft error" worry means141 * that it's probably better left alone until we have that142 * issue clarified.143 *144 * Note the PATH_MAX check - it's arbitrary but the real145 * kernel limit on a possible path component, not NAME_MAX,146 * which is the technical standard limit.147 */148static int verify_dirent_name(const char *name, int len)149{150 if (len <= 0 || len >= PATH_MAX)151 return -EIO;152 if (memchr(name, '/', len))153 return -EIO;154 return 0;155}156 157/*158 * Traditional linux readdir() handling..159 *160 * "count=1" is a special case, meaning that the buffer is one161 * dirent-structure in size and that the code can't handle more162 * anyway. Thus the special "fillonedir()" function for that163 * case (the low-level handlers don't need to care about this).164 */165 166#ifdef __ARCH_WANT_OLD_READDIR167 168struct old_linux_dirent {169 unsigned long d_ino;170 unsigned long d_offset;171 unsigned short d_namlen;172 char d_name[];173};174 175struct readdir_callback {176 struct dir_context ctx;177 struct old_linux_dirent __user * dirent;178 int result;179};180 181static bool fillonedir(struct dir_context *ctx, const char *name, int namlen,182 loff_t offset, u64 ino, unsigned int d_type)183{184 struct readdir_callback *buf =185 container_of(ctx, struct readdir_callback, ctx);186 struct old_linux_dirent __user * dirent;187 unsigned long d_ino;188 189 if (buf->result)190 return false;191 buf->result = verify_dirent_name(name, namlen);192 if (buf->result)193 return false;194 d_ino = ino;195 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {196 buf->result = -EOVERFLOW;197 return false;198 }199 buf->result++;200 dirent = buf->dirent;201 if (!user_write_access_begin(dirent,202 (unsigned long)(dirent->d_name + namlen + 1) -203 (unsigned long)dirent))204 goto efault;205 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);206 unsafe_put_user(offset, &dirent->d_offset, efault_end);207 unsafe_put_user(namlen, &dirent->d_namlen, efault_end);208 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);209 user_write_access_end();210 return true;211efault_end:212 user_write_access_end();213efault:214 buf->result = -EFAULT;215 return false;216}217 218SYSCALL_DEFINE3(old_readdir, unsigned int, fd,219 struct old_linux_dirent __user *, dirent, unsigned int, count)220{221 int error;222 struct fd f = fdget_pos(fd);223 struct readdir_callback buf = {224 .ctx.actor = fillonedir,225 .dirent = dirent226 };227 228 if (!fd_file(f))229 return -EBADF;230 231 error = iterate_dir(fd_file(f), &buf.ctx);232 if (buf.result)233 error = buf.result;234 235 fdput_pos(f);236 return error;237}238 239#endif /* __ARCH_WANT_OLD_READDIR */240 241/*242 * New, all-improved, singing, dancing, iBCS2-compliant getdents()243 * interface. 244 */245struct linux_dirent {246 unsigned long d_ino;247 unsigned long d_off;248 unsigned short d_reclen;249 char d_name[];250};251 252struct getdents_callback {253 struct dir_context ctx;254 struct linux_dirent __user * current_dir;255 int prev_reclen;256 int count;257 int error;258};259 260static bool filldir(struct dir_context *ctx, const char *name, int namlen,261 loff_t offset, u64 ino, unsigned int d_type)262{263 struct linux_dirent __user *dirent, *prev;264 struct getdents_callback *buf =265 container_of(ctx, struct getdents_callback, ctx);266 unsigned long d_ino;267 int reclen = ALIGN(offsetof(struct linux_dirent, d_name) + namlen + 2,268 sizeof(long));269 int prev_reclen;270 271 buf->error = verify_dirent_name(name, namlen);272 if (unlikely(buf->error))273 return false;274 buf->error = -EINVAL; /* only used if we fail.. */275 if (reclen > buf->count)276 return false;277 d_ino = ino;278 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {279 buf->error = -EOVERFLOW;280 return false;281 }282 prev_reclen = buf->prev_reclen;283 if (prev_reclen && signal_pending(current))284 return false;285 dirent = buf->current_dir;286 prev = (void __user *) dirent - prev_reclen;287 if (!user_write_access_begin(prev, reclen + prev_reclen))288 goto efault;289 290 /* This might be 'dirent->d_off', but if so it will get overwritten */291 unsafe_put_user(offset, &prev->d_off, efault_end);292 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);293 unsafe_put_user(reclen, &dirent->d_reclen, efault_end);294 unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);295 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);296 user_write_access_end();297 298 buf->current_dir = (void __user *)dirent + reclen;299 buf->prev_reclen = reclen;300 buf->count -= reclen;301 return true;302efault_end:303 user_write_access_end();304efault:305 buf->error = -EFAULT;306 return false;307}308 309SYSCALL_DEFINE3(getdents, unsigned int, fd,310 struct linux_dirent __user *, dirent, unsigned int, count)311{312 struct fd f;313 struct getdents_callback buf = {314 .ctx.actor = filldir,315 .count = count,316 .current_dir = dirent317 };318 int error;319 320 f = fdget_pos(fd);321 if (!fd_file(f))322 return -EBADF;323 324 error = iterate_dir(fd_file(f), &buf.ctx);325 if (error >= 0)326 error = buf.error;327 if (buf.prev_reclen) {328 struct linux_dirent __user * lastdirent;329 lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;330 331 if (put_user(buf.ctx.pos, &lastdirent->d_off))332 error = -EFAULT;333 else334 error = count - buf.count;335 }336 fdput_pos(f);337 return error;338}339 340struct getdents_callback64 {341 struct dir_context ctx;342 struct linux_dirent64 __user * current_dir;343 int prev_reclen;344 int count;345 int error;346};347 348static bool filldir64(struct dir_context *ctx, const char *name, int namlen,349 loff_t offset, u64 ino, unsigned int d_type)350{351 struct linux_dirent64 __user *dirent, *prev;352 struct getdents_callback64 *buf =353 container_of(ctx, struct getdents_callback64, ctx);354 int reclen = ALIGN(offsetof(struct linux_dirent64, d_name) + namlen + 1,355 sizeof(u64));356 int prev_reclen;357 358 buf->error = verify_dirent_name(name, namlen);359 if (unlikely(buf->error))360 return false;361 buf->error = -EINVAL; /* only used if we fail.. */362 if (reclen > buf->count)363 return false;364 prev_reclen = buf->prev_reclen;365 if (prev_reclen && signal_pending(current))366 return false;367 dirent = buf->current_dir;368 prev = (void __user *)dirent - prev_reclen;369 if (!user_write_access_begin(prev, reclen + prev_reclen))370 goto efault;371 372 /* This might be 'dirent->d_off', but if so it will get overwritten */373 unsafe_put_user(offset, &prev->d_off, efault_end);374 unsafe_put_user(ino, &dirent->d_ino, efault_end);375 unsafe_put_user(reclen, &dirent->d_reclen, efault_end);376 unsafe_put_user(d_type, &dirent->d_type, efault_end);377 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);378 user_write_access_end();379 380 buf->prev_reclen = reclen;381 buf->current_dir = (void __user *)dirent + reclen;382 buf->count -= reclen;383 return true;384 385efault_end:386 user_write_access_end();387efault:388 buf->error = -EFAULT;389 return false;390}391 392SYSCALL_DEFINE3(getdents64, unsigned int, fd,393 struct linux_dirent64 __user *, dirent, unsigned int, count)394{395 struct fd f;396 struct getdents_callback64 buf = {397 .ctx.actor = filldir64,398 .count = count,399 .current_dir = dirent400 };401 int error;402 403 f = fdget_pos(fd);404 if (!fd_file(f))405 return -EBADF;406 407 error = iterate_dir(fd_file(f), &buf.ctx);408 if (error >= 0)409 error = buf.error;410 if (buf.prev_reclen) {411 struct linux_dirent64 __user * lastdirent;412 typeof(lastdirent->d_off) d_off = buf.ctx.pos;413 414 lastdirent = (void __user *) buf.current_dir - buf.prev_reclen;415 if (put_user(d_off, &lastdirent->d_off))416 error = -EFAULT;417 else418 error = count - buf.count;419 }420 fdput_pos(f);421 return error;422}423 424#ifdef CONFIG_COMPAT425struct compat_old_linux_dirent {426 compat_ulong_t d_ino;427 compat_ulong_t d_offset;428 unsigned short d_namlen;429 char d_name[];430};431 432struct compat_readdir_callback {433 struct dir_context ctx;434 struct compat_old_linux_dirent __user *dirent;435 int result;436};437 438static bool compat_fillonedir(struct dir_context *ctx, const char *name,439 int namlen, loff_t offset, u64 ino,440 unsigned int d_type)441{442 struct compat_readdir_callback *buf =443 container_of(ctx, struct compat_readdir_callback, ctx);444 struct compat_old_linux_dirent __user *dirent;445 compat_ulong_t d_ino;446 447 if (buf->result)448 return false;449 buf->result = verify_dirent_name(name, namlen);450 if (buf->result)451 return false;452 d_ino = ino;453 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {454 buf->result = -EOVERFLOW;455 return false;456 }457 buf->result++;458 dirent = buf->dirent;459 if (!user_write_access_begin(dirent,460 (unsigned long)(dirent->d_name + namlen + 1) -461 (unsigned long)dirent))462 goto efault;463 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);464 unsafe_put_user(offset, &dirent->d_offset, efault_end);465 unsafe_put_user(namlen, &dirent->d_namlen, efault_end);466 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);467 user_write_access_end();468 return true;469efault_end:470 user_write_access_end();471efault:472 buf->result = -EFAULT;473 return false;474}475 476COMPAT_SYSCALL_DEFINE3(old_readdir, unsigned int, fd,477 struct compat_old_linux_dirent __user *, dirent, unsigned int, count)478{479 int error;480 struct fd f = fdget_pos(fd);481 struct compat_readdir_callback buf = {482 .ctx.actor = compat_fillonedir,483 .dirent = dirent484 };485 486 if (!fd_file(f))487 return -EBADF;488 489 error = iterate_dir(fd_file(f), &buf.ctx);490 if (buf.result)491 error = buf.result;492 493 fdput_pos(f);494 return error;495}496 497struct compat_linux_dirent {498 compat_ulong_t d_ino;499 compat_ulong_t d_off;500 unsigned short d_reclen;501 char d_name[];502};503 504struct compat_getdents_callback {505 struct dir_context ctx;506 struct compat_linux_dirent __user *current_dir;507 int prev_reclen;508 int count;509 int error;510};511 512static bool compat_filldir(struct dir_context *ctx, const char *name, int namlen,513 loff_t offset, u64 ino, unsigned int d_type)514{515 struct compat_linux_dirent __user *dirent, *prev;516 struct compat_getdents_callback *buf =517 container_of(ctx, struct compat_getdents_callback, ctx);518 compat_ulong_t d_ino;519 int reclen = ALIGN(offsetof(struct compat_linux_dirent, d_name) +520 namlen + 2, sizeof(compat_long_t));521 int prev_reclen;522 523 buf->error = verify_dirent_name(name, namlen);524 if (unlikely(buf->error))525 return false;526 buf->error = -EINVAL; /* only used if we fail.. */527 if (reclen > buf->count)528 return false;529 d_ino = ino;530 if (sizeof(d_ino) < sizeof(ino) && d_ino != ino) {531 buf->error = -EOVERFLOW;532 return false;533 }534 prev_reclen = buf->prev_reclen;535 if (prev_reclen && signal_pending(current))536 return false;537 dirent = buf->current_dir;538 prev = (void __user *) dirent - prev_reclen;539 if (!user_write_access_begin(prev, reclen + prev_reclen))540 goto efault;541 542 unsafe_put_user(offset, &prev->d_off, efault_end);543 unsafe_put_user(d_ino, &dirent->d_ino, efault_end);544 unsafe_put_user(reclen, &dirent->d_reclen, efault_end);545 unsafe_put_user(d_type, (char __user *) dirent + reclen - 1, efault_end);546 unsafe_copy_dirent_name(dirent->d_name, name, namlen, efault_end);547 user_write_access_end();548 549 buf->prev_reclen = reclen;550 buf->current_dir = (void __user *)dirent + reclen;551 buf->count -= reclen;552 return true;553efault_end:554 user_write_access_end();555efault:556 buf->error = -EFAULT;557 return false;558}559 560COMPAT_SYSCALL_DEFINE3(getdents, unsigned int, fd,561 struct compat_linux_dirent __user *, dirent, unsigned int, count)562{563 struct fd f;564 struct compat_getdents_callback buf = {565 .ctx.actor = compat_filldir,566 .current_dir = dirent,567 .count = count568 };569 int error;570 571 f = fdget_pos(fd);572 if (!fd_file(f))573 return -EBADF;574 575 error = iterate_dir(fd_file(f), &buf.ctx);576 if (error >= 0)577 error = buf.error;578 if (buf.prev_reclen) {579 struct compat_linux_dirent __user * lastdirent;580 lastdirent = (void __user *)buf.current_dir - buf.prev_reclen;581 582 if (put_user(buf.ctx.pos, &lastdirent->d_off))583 error = -EFAULT;584 else585 error = count - buf.count;586 }587 fdput_pos(f);588 return error;589}590#endif591