Re: [PATCH] ext4: fix WARNING in lock_two_nondirectories

Baokun Li
2023-12-25T01:39:04Z

On 2023/12/24 19:53, Edward Adam Davis wrote:
> If inode is the ext4 boot loader inode, then when it is a directory, the inode
> should also be set to bad inode.
>
> Reported-and-tested-by: syzbot+2c4a3b922a860084cc7f@syzkaller.appspotmail.com
> Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> ---
> fs/ext4/inode.c | 8 ++++++--
> 1 file changed, 6 insertions(+), 2 deletions(-)
>
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index 61277f7f8722..b311f610f008 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4944,8 +4944,12 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
> inode->i_fop = &ext4_file_operations;
> ext4_set_aops(inode);
> } else if (S_ISDIR(inode->i_mode)) {
> - inode->i_op = &ext4_dir_inode_operations;
> - inode->i_fop = &ext4_dir_operations;
> + if (ino == EXT4_BOOT_LOADER_INO)
> + make_bad_inode(inode);
Marking the boot loader inode as a bad inode here is useless,
EXT4_IGET_BAD allows us to get a bad boot loader inode.
In my opinion, it doesn't make sense to call lock_two_nondirectories()
here to determine if the inode is a regular file or not, since the logic
for dealing with non-regular files comes after the locking, so calling
lock_two_inodes() directly here will suffice.

Merry Christmas!
Baokun
> + else {
> + inode->i_op = &ext4_dir_inode_operations;
> + inode->i_fop = &ext4_dir_operations;
> + }
> } else if (S_ISLNK(inode->i_mode)) {
> /* VFS does not allow setting these so must be corruption */
> if (IS_APPEND(inode) || IS_IMMUTABLE(inode)) {