NFSD: Refactor nfsd_setuser_and_check_port()

There are several places where __fh_verify unconditionally dereferences
rqstp to check that the connection is suitably secure.  They look at
rqstp->rq_xprt which is not meaningful in the target use case of
"localio" NFS in which the client talks directly to the local server.

Prepare these to always succeed when rqstp is NULL.
Signed-off-by: NeilBrown <neilb@suse.de>
Co-developed-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Anna Schumaker <anna.schumaker@oracle.com>

fs/nfsd/nfsfh.c

@@ -87,23 +87,24 @@ nfsd_mode_check(struct dentry *dentry, umode_t requested)
 	return nfserr_wrong_type;
 }
 
-static bool nfsd_originating_port_ok(struct svc_rqst *rqstp, int flags)
+static bool nfsd_originating_port_ok(struct svc_rqst *rqstp,
+				     struct svc_cred *cred,
+				     struct svc_export *exp)
 {
-	if (flags & NFSEXP_INSECURE_PORT)
+	if (nfsexp_flags(cred, exp) & NFSEXP_INSECURE_PORT)
 		return true;
 	/* We don't require gss requests to use low ports: */
-	if (rqstp->rq_cred.cr_flavor >= RPC_AUTH_GSS)
+	if (cred->cr_flavor >= RPC_AUTH_GSS)
 		return true;
 	return test_bit(RQ_SECURE, &rqstp->rq_flags);
 }
 
 static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
+					  struct svc_cred *cred,
 					  struct svc_export *exp)
 {
-	int flags = nfsexp_flags(&rqstp->rq_cred, exp);
-
 	/* Check if the request originated from a secure port. */
-	if (!nfsd_originating_port_ok(rqstp, flags)) {
+	if (rqstp && !nfsd_originating_port_ok(rqstp, cred, exp)) {
 		RPC_IFDEBUG(char buf[RPC_MAX_ADDRBUFLEN]);
 		dprintk("nfsd: request from insecure port %s!\n",
 		        svc_print_addr(rqstp, buf, sizeof(buf)));
@@ -111,7 +112,7 @@ static __be32 nfsd_setuser_and_check_port(struct svc_rqst *rqstp,
 	}
 
 	/* Set user creds for this exportpoint */
-	return nfserrno(nfsd_setuser(&rqstp->rq_cred, exp));
+	return nfserrno(nfsd_setuser(cred, exp));
 }
 
 static inline __be32 check_pseudo_root(struct dentry *dentry,
@@ -219,7 +220,7 @@ static __be32 nfsd_set_fh_dentry(struct svc_rqst *rqstp, struct svc_fh *fhp)
 		put_cred(override_creds(new));
 		put_cred(new);
 	} else {
-		error = nfsd_setuser_and_check_port(rqstp, exp);
+		error = nfsd_setuser_and_check_port(rqstp, &rqstp->rq_cred, exp);
 		if (error)
 			goto out;
 	}
@@ -358,7 +359,7 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, umode_t type, int access)
 	if (error)
 		goto out;
 
-	error = nfsd_setuser_and_check_port(rqstp, exp);
+	error = nfsd_setuser_and_check_port(rqstp, &rqstp->rq_cred, exp);
 	if (error)
 		goto out;