FAILED: Patch "nfsd: fix return error code for nfsd_map_name_to_[ug]id" failed to apply to 5.10-stable tree

The patch below does not apply to the 5.10-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

Thanks,
Sasha

------------------ original commit in Linus's tree ------------------

From 404d779466646bf1461f2090ff137e99acaecf42 Mon Sep 17 00:00:00 2001
From: Anthony Iliopoulos <[email protected]>
Date: Mon, 22 Dec 2025 14:30:05 -0500
Subject: [PATCH] nfsd: fix return error code for nfsd_map_name_to_[ug]id

idmap lookups can time out while the cache is waiting for a userspace upcall reply. In that case cache_check() returns -ETIMEDOUT to callers.

The nfsd_map_name_to_[ug]id functions currently proceed with attempting to map the id to a kuid despite a potentially temporary failure to perform the idmap lookup. This results in the code returning the error NFSERR_BADOWNER which can cause client operations to return to userspace with failure.

Fix this by returning the failure status before attempting kuid mapping.

This will return NFSERR_JUKEBOX on idmap lookup timeout so that clients can retry the operation instead of aborting it.

---
 fs/nfsd/nfs4idmap.c | 4 ++++
 1 file changed, 4 insertions(+)

index b5b3d45979c9b..c319c31b0f647 100644
@@ -672,6 +672,8 @@ __be32 nfsd_map_name_to_uid(struct svc_rqst *rqstp, const char *name,
 		return nfserr_inval;
 
 	status = do_name_to_id(rqstp, IDMAP_TYPE_USER, name, namelen, &id);
+	if (status)
+		return status;
 	*uid = make_kuid(nfsd_user_namespace(rqstp), id);
 	if (!uid_valid(*uid))
 		status = nfserr_badowner;

@@ -707,6 +709,8 @@ __be32 nfsd_map_name_to_gid(struct svc_rqst *rqstp, const char *name,
 		return nfserr_inval;
 
 	status = do_name_to_id(rqstp, IDMAP_TYPE_GROUP, name, namelen, &id);
+	if (status)
+		return status;
 	*gid = make_kgid(nfsd_user_namespace(rqstp), id);
 	if (!gid_valid(*gid))
 		status = nfserr_badowner;

2.51.0