NFS client bugfixes for Linux 5.1

Highlights include:
 
 Bugfixes:
 - Fix an Oops in SUNRPC back channel tracepoints
 - Fix a SUNRPC client regression when handling oversized replies
 - Fix the minimal size for SUNRPC reply buffer allocation
 - rpc_decode_header() must always return a non-zero value on error
 - Fix a typo in pnfs_update_layout()
 
 Cleanups:
 - Remove redundant check for the reply length in call_decode()
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Merge tag 'nfs-for-5.1-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs

Pull NFS client bugfixes from Trond Myklebust:
 "Highlights include:

  Bugfixes:
   - Fix an Oops in SUNRPC back channel tracepoints
   - Fix a SUNRPC client regression when handling oversized replies
   - Fix the minimal size for SUNRPC reply buffer allocation
   - rpc_decode_header() must always return a non-zero value on error
   - Fix a typo in pnfs_update_layout()

  Cleanup:
   - Remove redundant check for the reply length in call_decode()"

* tag 'nfs-for-5.1-2' of git://git.linux-nfs.org/projects/trondmy/linux-nfs:
  SUNRPC: Remove redundant check for the reply length in call_decode()
  SUNRPC: Handle the SYSTEM_ERR rpc error
  SUNRPC: rpc_decode_header() must always return a non-zero value on error
  SUNRPC: Use the ENOTCONN error on socket disconnect
  SUNRPC: Fix the minimal size for reply buffer allocation
  SUNRPC: Fix a client regression when handling oversized replies
  pNFS: Fix a typo in pnfs_update_layout
  fix null pointer deref in tracepoints in back channel

fs/nfs/pnfs.c

@@ -1889,7 +1889,7 @@ lookup_again:
 	    atomic_read(&lo->plh_outstanding) != 0) {
 		spin_unlock(&ino->i_lock);
 		lseg = ERR_PTR(wait_var_event_killable(&lo->plh_outstanding,
-					atomic_read(&lo->plh_outstanding)));
+					!atomic_read(&lo->plh_outstanding)));
 		if (IS_ERR(lseg) || !list_empty(&lo->plh_segs))
 			goto out_put_layout_hdr;
 		pnfs_put_layout_hdr(lo);

include/trace/events/sunrpc.h

@@ -712,7 +712,8 @@ TRACE_EVENT(xprt_transmit,
 
 	TP_fast_assign(
 		__entry->task_id = rqst->rq_task->tk_pid;
-		__entry->client_id = rqst->rq_task->tk_client->cl_clid;
+		__entry->client_id = rqst->rq_task->tk_client ?
+			rqst->rq_task->tk_client->cl_clid : -1;
 		__entry->xid = be32_to_cpu(rqst->rq_xid);
 		__entry->seqno = rqst->rq_seqno;
 		__entry->status = status;
@@ -742,7 +743,8 @@ TRACE_EVENT(xprt_enq_xmit,
 
 	TP_fast_assign(
 		__entry->task_id = task->tk_pid;
-		__entry->client_id = task->tk_client->cl_clid;
+		__entry->client_id = task->tk_client ?
+			task->tk_client->cl_clid : -1;
 		__entry->xid = be32_to_cpu(task->tk_rqstp->rq_xid);
 		__entry->seqno = task->tk_rqstp->rq_seqno;
 		__entry->stage = stage;

net/sunrpc/clnt.c

@@ -1730,7 +1730,12 @@ call_allocate(struct rpc_task *task)
 	req->rq_callsize = RPC_CALLHDRSIZE + (auth->au_cslack << 1) +
 			   proc->p_arglen;
 	req->rq_callsize <<= 2;
-	req->rq_rcvsize = RPC_REPHDRSIZE + auth->au_rslack + proc->p_replen;
+	/*
+	 * Note: the reply buffer must at minimum allocate enough space
+	 * for the 'struct accepted_reply' from RFC5531.
+	 */
+	req->rq_rcvsize = RPC_REPHDRSIZE + auth->au_rslack + \
+			max_t(size_t, proc->p_replen, 2);
 	req->rq_rcvsize <<= 2;
 
 	status = xprt->ops->buf_alloc(task);
@@ -2387,9 +2392,6 @@ call_decode(struct rpc_task *task)
 	WARN_ON(memcmp(&req->rq_rcv_buf, &req->rq_private_buf,
 				sizeof(req->rq_rcv_buf)) != 0);
 
-	if (req->rq_rcv_buf.len < 12)
-		goto out_retry;
-
 	xdr_init_decode(&xdr, &req->rq_rcv_buf,
 			req->rq_rcv_buf.head[0].iov_base, req);
 	switch (rpc_decode_header(task, &xdr)) {
@@ -2400,7 +2402,6 @@ call_decode(struct rpc_task *task)
 			task->tk_pid, __func__, task->tk_status);
 		return;
 	case -EAGAIN:
-out_retry:
 		task->tk_status = 0;
 		/* Note: rpc_decode_header() may have freed the RPC slot */
 		if (task->tk_rqstp == req) {
@@ -2449,7 +2450,7 @@ static noinline int
 rpc_decode_header(struct rpc_task *task, struct xdr_stream *xdr)
 {
 	struct rpc_clnt *clnt = task->tk_client;
-	int error = -EACCES;
+	int error;
 	__be32 *p;
 
 	/* RFC-1014 says that the representation of XDR data must be a
@@ -2458,7 +2459,7 @@ rpc_decode_header(struct rpc_task *task, struct xdr_stream *xdr)
 	 *   undefined results
 	 */
 	if (task->tk_rqstp->rq_rcv_buf.len & 3)
-		goto out_badlen;
+		goto out_unparsable;
 
 	p = xdr_inline_decode(xdr, 3 * sizeof(*p));
 	if (!p)
@@ -2492,10 +2493,12 @@ rpc_decode_header(struct rpc_task *task, struct xdr_stream *xdr)
 		error = -EOPNOTSUPP;
 		goto out_err;
 	case rpc_garbage_args:
+	case rpc_system_err:
 		trace_rpc__garbage_args(task);
+		error = -EIO;
 		break;
 	default:
-		trace_rpc__unparsable(task);
+		goto out_unparsable;
 	}
 
 out_garbage:
@@ -2509,11 +2512,6 @@ out_err:
 	rpc_exit(task, error);
 	return error;
 
-out_badlen:
-	trace_rpc__unparsable(task);
-	error = -EIO;
-	goto out_err;
-
 out_unparsable:
 	trace_rpc__unparsable(task);
 	error = -EIO;
@@ -2524,6 +2522,7 @@ out_verifier:
 	goto out_garbage;
 
 out_msg_denied:
+	error = -EACCES;
 	p = xdr_inline_decode(xdr, sizeof(*p));
 	if (!p)
 		goto out_unparsable;
@@ -2535,9 +2534,7 @@ out_msg_denied:
 		error = -EPROTONOSUPPORT;
 		goto out_err;
 	default:
-		trace_rpc__unparsable(task);
-		error = -EIO;
-		goto out_err;
+		goto out_unparsable;
 	}
 
 	p = xdr_inline_decode(xdr, sizeof(*p));
@@ -2572,8 +2569,7 @@ out_msg_denied:
 			task->tk_xprt->servername);
 		break;
 	default:
-		trace_rpc__unparsable(task);
-		error = -EIO;
+		goto out_unparsable;
 	}
 	goto out_err;
 }

net/sunrpc/xprt.c

@@ -664,7 +664,7 @@ void xprt_disconnect_done(struct rpc_xprt *xprt)
 	spin_lock_bh(&xprt->transport_lock);
 	xprt_clear_connected(xprt);
 	xprt_clear_write_space_locked(xprt);
-	xprt_wake_pending_tasks(xprt, -EAGAIN);
+	xprt_wake_pending_tasks(xprt, -ENOTCONN);
 	spin_unlock_bh(&xprt->transport_lock);
 }
 EXPORT_SYMBOL_GPL(xprt_disconnect_done);

net/sunrpc/xprtsock.c

@@ -453,7 +453,7 @@ xs_read_xdr_buf(struct socket *sock, struct msghdr *msg, int flags,
 			goto out;
 		if (ret != want)
 			goto out;
-	} else
+	} else if (offset < seek_init)
 		offset = seek_init;
 	ret = -EMSGSIZE;
 out: