[PATCH v2 2/2] nfsd: fix return error code for nfsd_map_name_to_[ug]id

[Chuck Lever <cel@kernel.org>]

From: Anthony Iliopoulos <ailiop@suse.com>

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.

Fixes: 65e10f6d0ab0 ("nfsd: Convert idmap to use kuids and kgids")
X-Cc: stable@vger.kernel.org
Signed-off-by: Anthony Iliopoulos <ailiop@suse.com>
Reviewed-by: NeilBrown <neil@brown.name>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
---
 fs/nfsd/nfs4idmap.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/nfsd/nfs4idmap.c b/fs/nfsd/nfs4idmap.c
index b5b3d45979c9..c319c31b0f64 100644
--- a/fs/nfsd/nfs4idmap.c
+++ b/fs/nfsd/nfs4idmap.c
@@ -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;
-- 
2.52.0