diff options
| author | Zhiyu Zhang <zhiyuzhang999@gmail.com> | 2026-01-01 19:11:48 +0800 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2026-03-04 07:19:34 -0500 |
| commit | 7fe0de287e931e07cb96ecf1f449b2ebdb0e1115 (patch) | |
| tree | 6680871c156c4a684dc7e887c602a9b2fbc85754 /fs | |
| parent | b9abb760db20504240a7147f27934d900cd80b23 (diff) | |
fat: avoid parent link count underflow in rmdir
[ Upstream commit 8cafcb881364af5ef3a8b9fed4db254054033d8a ]
Corrupted FAT images can leave a directory inode with an incorrect
i_nlink (e.g. 2 even though subdirectories exist). rmdir then
unconditionally calls drop_nlink(dir) and can drive i_nlink to 0,
triggering the WARN_ON in drop_nlink().
Add a sanity check in vfat_rmdir() and msdos_rmdir(): only drop the
parent link count when it is at least 3, otherwise report a filesystem
error.
Link: https://lkml.kernel.org/r/20260101111148.1437-1-zhiyuzhang999@gmail.com
Fixes: 9a53c3a783c2 ("[PATCH] r/o bind mounts: unlink: monitor i_nlink")
Signed-off-by: Zhiyu Zhang <zhiyuzhang999@gmail.com>
Reported-by: Zhiyu Zhang <zhiyuzhang999@gmail.com>
Closes: https://lore.kernel.org/linux-fsdevel/aVN06OKsKxZe6-Kv@casper.infradead.org/T/#t
Tested-by: Zhiyu Zhang <zhiyuzhang999@gmail.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'fs')
| -rw-r--r-- | fs/fat/namei_msdos.c | 7 | ||||
| -rw-r--r-- | fs/fat/namei_vfat.c | 7 |
2 files changed, 12 insertions, 2 deletions
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c index 9d062886fbc1..63a323be9179 100644 --- a/fs/fat/namei_msdos.c +++ b/fs/fat/namei_msdos.c @@ -325,7 +325,12 @@ static int msdos_rmdir(struct inode *dir, struct dentry *dentry) err = fat_remove_entries(dir, &sinfo); /* and releases bh */ if (err) goto out; - drop_nlink(dir); + if (dir->i_nlink >= 3) + drop_nlink(dir); + else { + fat_fs_error(sb, "parent dir link count too low (%u)", + dir->i_nlink); + } clear_nlink(inode); fat_truncate_time(inode, NULL, S_CTIME); diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c index 9bc7d1602c15..2a0d9a9c2c8f 100644 --- a/fs/fat/namei_vfat.c +++ b/fs/fat/namei_vfat.c @@ -808,7 +808,12 @@ static int vfat_rmdir(struct inode *dir, struct dentry *dentry) err = fat_remove_entries(dir, &sinfo); /* and releases bh */ if (err) goto out; - drop_nlink(dir); + if (dir->i_nlink >= 3) + drop_nlink(dir); + else { + fat_fs_error(sb, "parent dir link count too low (%u)", + dir->i_nlink); + } clear_nlink(inode); fat_truncate_time(inode, NULL, S_ATIME|S_MTIME); |