Re: [PATCH] xfs: Fix error pointer dereference

[Darrick J. Wong]

On Wed, Feb 18, 2026 at 01:51:15PM -0600, Ethan Tidmore wrote:
> The function try_lookup_noperm() can return an error pointer and is not
> checked for one. Add checks for error pointer.
> 
> Detected by Smatch:
> fs/xfs/scrub/orphanage.c:449 xrep_adoption_check_dcache() error: 
> 'd_child' dereferencing possible ERR_PTR()
> 
> fs/xfs/scrub/orphanage.c:485 xrep_adoption_zap_dcache() error: 
> 'd_child' dereferencing possible ERR_PTR()
> 
> Fixes: 06c567403ae5a ("Use try_lookup_noperm() instead of d_hash_and_lookup() outside of VFS")

Cc: <stable@xxxxxxxxxxxxxxx> # v6.16

> Signed-off-by: Ethan Tidmore <ethantidmore06@xxxxxxxxx>
> ---
>  fs/xfs/scrub/orphanage.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/xfs/scrub/orphanage.c b/fs/xfs/scrub/orphanage.c
> index 52a108f6d5f4..cdb0f486f50c 100644
> --- a/fs/xfs/scrub/orphanage.c
> +++ b/fs/xfs/scrub/orphanage.c
> @@ -442,7 +442,7 @@ xrep_adoption_check_dcache(
>  		return 0;
>  
>  	d_child = try_lookup_noperm(&qname, d_orphanage);

"Look up a dentry by name in the dcache, returning NULL if it does not
currently exist."

Could you please fix the documentation since try_lookup_noperm can
return ERR_PTR values?

> -	if (d_child) {
> +	if (!IS_ERR_OR_NULL(d_child)) {

If d_child is an ERR_PTR, shouldn't we extract that error value and
return it instead of zero?

--D

>  		trace_xrep_adoption_check_child(sc->mp, d_child);
>  
>  		if (d_is_positive(d_child)) {
> @@ -479,7 +479,7 @@ xrep_adoption_zap_dcache(
>  		return;
>  
>  	d_child = try_lookup_noperm(&qname, d_orphanage);
> -	while (d_child != NULL) {
> +	while (!IS_ERR_OR_NULL(d_child)) {
>  		trace_xrep_adoption_invalidate_child(sc->mp, d_child);
>  
>  		ASSERT(d_is_negative(d_child));
> -- 
> 2.53.0
> 
>