SUNRPC refactor rpcauth_checkverf error returns

Most of the time an error from the credops crvalidate function means the
server has sent us a garbage verifier. The gss_validate function is the
exception where there is an -EACCES case if the user GSS_context on the client
has expired.

Signed-off-by: Andy Adamson <[e-mail]>
Signed-off-by: Trond Myklebust <[e-mail]>

net/sunrpc/auth_gss/auth_gss.c

···
 	struct xdr_netobj mic;
 	u32		flav,len;
 	u32		maj_stat;
+	__be32		*ret = ERR_PTR(-EIO);
 
 	dprintk("RPC: %5u %s\n", task->tk_pid, __func__);
 
···
 	mic.data = (u8 *)p;
 	mic.len = len;
 
+	ret = ERR_PTR(-EACCES);
 	maj_stat = gss_verify_mic(ctx->gc_gss_ctx, &verf_buf, &mic);
 	if (maj_stat == GSS_S_CONTEXT_EXPIRED)
 		clear_bit(RPCAUTH_CRED_UPTODATE, &cred->cr_flags);
···
 	return p + XDR_QUADLEN(len);
 out_bad:
 	gss_put_ctx(ctx);
-	dprintk("RPC: %5u %s failed.\n", task->tk_pid, __func__);
-	return NULL;
+	dprintk("RPC: %5u %s failed ret %ld.\n", task->tk_pid, __func__,
+		PTR_ERR(ret));
+	return ret;
 }
 
 static void gss_wrap_req_encode(kxdreproc_t encode, struct rpc_rqst *rqstp,

net/sunrpc/auth_null.c

···
 	flavor = ntohl(*p++);
 	if (flavor != RPC_AUTH_NULL) {
 		printk("RPC: bad verf flavor: %u\n", flavor);
-		return NULL;
+		return ERR_PTR(-EIO);
 	}
 
 	size = ntohl(*p++);
 	if (size != 0) {
 		printk("RPC: bad verf size: %u\n", size);
-		return NULL;
+		return ERR_PTR(-EIO);
 	}
 
 	return p;

net/sunrpc/auth_unix.c

···
 	    flavor != RPC_AUTH_UNIX &&
 	    flavor != RPC_AUTH_SHORT) {
 		printk("RPC: bad verf flavor: %u\n", flavor);
-		return NULL;
+		return ERR_PTR(-EIO);
 	}
 
 	size = ntohl(*p++);
 	if (size > RPC_MAX_AUTH_SIZE) {
 		printk("RPC: giant verf size: %u\n", size);
-		return NULL;
+		return ERR_PTR(-EIO);
 	}
 	task->tk_rqstp->rq_cred->cr_auth->au_rslack = (size >> 2) + 2;
 	p += (size >> 2);

net/sunrpc/clnt.c

···
 		dprintk("RPC: %5u %s: XDR representation not a multiple of"
 		       " 4 bytes: 0x%x\n", task->tk_pid, __func__,
 		       task->tk_rqstp->rq_rcv_buf.len);
-		goto out_eio;
+		error = -EIO;
+		goto out_err;
 	}
 	if ((len -= 3) < 0)
 		goto out_overflow;
···
 	if ((n = ntohl(*p++)) != RPC_REPLY) {
 		dprintk("RPC: %5u %s: not an RPC reply: %x\n",
 			task->tk_pid, __func__, n);
+		error = -EIO;
 		goto out_garbage;
 	}
 
···
 			dprintk("RPC: %5u %s: RPC call rejected, "
 				"unknown error: %x\n",
 				task->tk_pid, __func__, n);
-			goto out_eio;
+			error = -EIO;
+			goto out_err;
 		}
 		if (--len < 0)
 			goto out_overflow;
···
 				task->tk_pid, __func__, n);
 		goto out_err;
 	}
-	if (!(p = rpcauth_checkverf(task, p))) {
-		dprintk("RPC: %5u %s: auth check failed\n",
-				task->tk_pid, __func__);
+	p = rpcauth_checkverf(task, p);
+	if (IS_ERR(p)) {
+		error = PTR_ERR(p);
+		dprintk("RPC: %5u %s: auth check failed with %d\n",
+				task->tk_pid, __func__, error);
 		goto out_garbage;		/* bad verifier, retry */
 	}
 	len = p - (__be32 *)iov->iov_base - 1;
···
 out_retry:
 		return ERR_PTR(-EAGAIN);
 	}
-out_eio:
-	error = -EIO;
 out_err:
 	rpc_exit(task, error);
 	dprintk("RPC: %5u %s: call failed with error %d\n", task->tk_pid,