From: Zhiyu Zhang <zhiyuzhang999@gmail.com> mainline inclusion from mainline-v7.0-rc1 commit 8cafcb881364af5ef3a8b9fed4db254054033d8a category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/13898 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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/... 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: Yongjian Sun <sunyongjian1@huawei.com> --- fs/fat/namei_msdos.c | 7 ++++++- 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 0cdd0fb9f742..db9a88fb6e2d 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); -- 2.39.2