nfsd: fix access checking for NLM under XPRTSEC policies

JIRA: https://issues.redhat.com/browse/RHEL-82689

commit 0813c5f
Author: Olga Kornievskaia <okorniev@redhat.com>
Date:   Fri Mar 21 20:13:04 2025 -0400

    nfsd: fix access checking for NLM under XPRTSEC policies

    When an export policy with xprtsec policy is set with "tls"
    and/or "mtls", but an NFS client is doing a v3 xprtsec=tls
    mount, then NLM locking calls fail with an error because
    there is currently no support for NLM with TLS.

    Until such support is added, allow NLM calls under TLS-secured
    policy.

    Fixes: 4cc9b9f ("nfsd: refine and rename NFSD_MAY_LOCK")
    Cc: stable@vger.kernel.org
    Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>
    Reviewed-by: NeilBrown <neil@brown.name>
    Reviewed-by: Jeff Layton <jlayton@kernel.org>
    Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

Signed-off-by: Olga Kornievskaia <okorniev@redhat.com>

Author: Olga Kornievskaia

fs/nfsd/export.c

@@ -1130,7 +1130,8 @@ __be32 check_nfsd_access(struct svc_export *exp, struct svc_rqst *rqstp,
 		    test_bit(XPT_PEER_AUTH, &xprt->xpt_flags))
 			goto ok;
 	}
-	goto denied;
+	if (!may_bypass_gss)
+		goto denied;
 
 ok:
 	/* legacy gss-only clients are always OK: */