SUNRPC: Fix a race in the receive code path
We must ensure that the call to rpc_sleep_on() in xprt_transmit() cannot
race with the call to xprt_complete_rqst().
Reported-by: Chuck Lever <chuck.lever@oracle.com>
Link: https://bugzilla.linux-nfs.org/show_bug.cgi?id=317
Fixes: ce7c252a8c74 ("SUNRPC: Add a separate spinlock to protect..")
Cc: stable@vger.kernel.org # 4.14+
Reviewed-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 02a9bac..5b06f69 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1001,6 +1001,7 @@
{
struct rpc_rqst *req = task->tk_rqstp;
struct rpc_xprt *xprt = req->rq_xprt;
+ unsigned int connect_cookie;
int status, numreqs;
dprintk("RPC: %5u xprt_transmit(%u)\n", task->tk_pid, req->rq_slen);
@@ -1024,6 +1025,7 @@
} else if (!req->rq_bytes_sent)
return;
+ connect_cookie = xprt->connect_cookie;
req->rq_xtime = ktime_get();
status = xprt->ops->send_request(task);
trace_xprt_transmit(xprt, req->rq_xid, status);
@@ -1047,20 +1049,28 @@
xprt->stat.bklog_u += xprt->backlog.qlen;
xprt->stat.sending_u += xprt->sending.qlen;
xprt->stat.pending_u += xprt->pending.qlen;
-
- /* Don't race with disconnect */
- if (!xprt_connected(xprt))
- task->tk_status = -ENOTCONN;
- else {
- /*
- * Sleep on the pending queue since
- * we're expecting a reply.
- */
- if (!req->rq_reply_bytes_recvd && rpc_reply_expected(task))
- rpc_sleep_on(&xprt->pending, task, xprt_timer);
- req->rq_connect_cookie = xprt->connect_cookie;
- }
spin_unlock_bh(&xprt->transport_lock);
+
+ req->rq_connect_cookie = connect_cookie;
+ if (rpc_reply_expected(task) && !READ_ONCE(req->rq_reply_bytes_recvd)) {
+ /*
+ * Sleep on the pending queue if we're expecting a reply.
+ * The spinlock ensures atomicity between the test of
+ * req->rq_reply_bytes_recvd, and the call to rpc_sleep_on().
+ */
+ spin_lock(&xprt->recv_lock);
+ if (!req->rq_reply_bytes_recvd) {
+ rpc_sleep_on(&xprt->pending, task, xprt_timer);
+ /*
+ * Send an extra queue wakeup call if the
+ * connection was dropped in case the call to
+ * rpc_sleep_on() raced.
+ */
+ if (!xprt_connected(xprt))
+ xprt_wake_pending_tasks(xprt, -ENOTCONN);
+ }
+ spin_unlock(&xprt->recv_lock);
+ }
}
static void xprt_add_backlog(struct rpc_xprt *xprt, struct rpc_task *task)