On Thu, Aug 14, 2025 at 12:37 AM André Almeida <andrealmeid@xxxxxxxxxx> wrote:
>
> In a overlayfs with casefold enabled, all new dentries should have
> casefold enabled as well. Check this at ovl_create_real()
>
> Signed-off-by: André Almeida <andrealmeid@xxxxxxxxxx>
> ---
> Changes from v3:
> - New patch
> ---
> fs/overlayfs/dir.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/fs/overlayfs/dir.c b/fs/overlayfs/dir.c
> index 70b8687dc45e8e33079c865ae302ac58464224a6..be8c5d02302de7a3ee63220a69f99a808fde3128 100644
> --- a/fs/overlayfs/dir.c
> +++ b/fs/overlayfs/dir.c
> @@ -187,6 +187,11 @@ struct dentry *ovl_create_real(struct ovl_fs *ofs, struct dentry *parent,
> /* mkdir is special... */
> newdentry = ovl_do_mkdir(ofs, dir, newdentry, attr->mode);
> err = PTR_ERR_OR_ZERO(newdentry);
> + /* expect to inherit casefolding from workdir/upperdir */
> + if (!err && ofs->casefold != ovl_dentry_casefolded(newdentry)) {
> + dput(newdentry);
> + err = -EINVAL;
> + }
If we do encounter a filesystem that does not inherit casefolding
(which is perfectly legal) the reason for this error is going to be very
hard for users to track down.
I think this calls for pr_warn_ratelimited() like we did for the lookup
warnings with inconsistent casefloding.
Thanks,
Amir.
