On Thu, Jan 26, 2023 at 12:22:21PM +0100, Jan Kara wrote:
> When we are renaming a directory to a different directory, we need to
> update '..' entry in the moved directory. However nothing prevents moved
> directory from being modified and even converted from the inline format
> to the normal format. When such race happens the rename code gets
> confused and we crash. Fix the problem by locking the moved directory.
Four months later, I have a question --
Is it necessary for ext4_cross_rename to inode_lock_nested on both
old.inode and new.inode? We're resetting the dotdot entries on both
children in that case, which means that we also need to lock out inline
data conversions, right?
--D
> CC: stable@xxxxxxxxxxxxxxx
> Fixes: 32f7f22c0b52 ("ext4: let ext4_rename handle inline dir")
> Signed-off-by: Jan Kara <jack@xxxxxxx>
> ---
> fs/ext4/namei.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
> diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> index dd28453d6ea3..270fbcba75b6 100644
> --- a/fs/ext4/namei.c
> +++ b/fs/ext4/namei.c
> @@ -3872,9 +3872,16 @@ static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
> if (new.dir != old.dir && EXT4_DIR_LINK_MAX(new.dir))
> goto end_rename;
> }
> + /*
> + * We need to protect against old.inode directory getting
> + * converted from inline directory format into a normal one.
> + */
> + inode_lock_nested(old.inode, I_MUTEX_NONDIR2);
> retval = ext4_rename_dir_prepare(handle, &old);
> - if (retval)
> + if (retval) {
> + inode_unlock(old.inode);
> goto end_rename;
> + }
> }
> /*
> * If we're renaming a file within an inline_data dir and adding or
> @@ -4006,6 +4013,8 @@ static int ext4_rename(struct user_namespace *mnt_userns, struct inode *old_dir,
> } else {
> ext4_journal_stop(handle);
> }
> + if (old.dir_bh)
> + inode_unlock(old.inode);
> release_bh:
> brelse(old.dir_bh);
> brelse(old.bh);
> --
> 2.35.3
>
