Re: [PATCH] ovl: fail ovl_lock_rename_workdir() if either target is unhashed

Amir Goldstein
2025-11-28T09:54:27Z

On Fri, Nov 28, 2025 at 2:22 AM NeilBrown <neilb@ownmail.net> wrote:
>
>
> From: NeilBrown <neil@brown.name>
>
> As well as checking that the parent hasn't changed after getting the
> lock we need to check that the dentry hasn't been unhashed.
> Otherwise we might try to rename something that has been removed.
>
> Reported-by: syzbot+bfc9a0ccf0de47d04e8c@syzkaller.appspotmail.com
> Fixes: d2c995581c7c ("ovl: Call ovl_create_temp() without lock held.")
> Signed-off-by: NeilBrown <neil@brown.name>

Reviewed-by: Amir Goldstein <amir73il@gmail.com>

> ---
> fs/overlayfs/util.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
> index f76672f2e686..82373dd1ce6e 100644
> --- a/fs/overlayfs/util.c
> +++ b/fs/overlayfs/util.c
> @@ -1234,9 +1234,9 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *work,
> goto err;
> if (trap)
> goto err_unlock;
> - if (work && work->d_parent != workdir)
> + if (work && (work->d_parent != workdir || d_unhashed(work)))
> goto err_unlock;
> - if (upper && upper->d_parent != upperdir)
> + if (upper && (upper->d_parent != upperdir || d_unhashed(upper)))
> goto err_unlock;
>
> return 0;
> --
> 2.50.0.107.gf914562f5916.dirty
>