[PATCH AUTOSEL 3.18 06/16] SUNRPC: Fix a potential race in xprt_connect()

Sasha Levin
2018-12-13T04:35:35Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit 0a9a4304f3614e25d9de9b63502ca633c01c0d70 ]

If an asynchronous connection attempt completes while another task is
in xprt_connect(), then the call to rpc_sleep_on() could end up
racing with the call to xprt_wake_pending_tasks().
So add a second test of the connection state after we've put the
task to sleep and set the XPRT_CONNECTING flag, when we know that there
can be no asynchronous connection attempts still in progress.

Fixes: 0b9e79431377d ("SUNRPC: Move the test for XPRT_CONNECTING into...")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/sunrpc/xprt.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index 56e4e150e80e..dca234b1f77d 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -721,8 +721,15 @@ void xprt_connect(struct rpc_task *task)
return;
if (xprt_test_and_set_connecting(xprt))
return;
- xprt->stat.connect_start = jiffies;
- xprt->ops->connect(xprt, task);
+ /* Race breaker */
+ if (!xprt_connected(xprt)) {
+ xprt->stat.connect_start = jiffies;
+ xprt->ops->connect(xprt, task);
+ } else {
+ xprt_clear_connecting(xprt);
+ task->tk_status = 0;
+ rpc_wake_up_queued_task(&xprt->pending, task);
+ }
}
}

--
2.19.1