SUNRPC: Ensure we release the socket write lock if the rpc_task exits early

If the rpc_task exits while holding the socket write lock before it has
allocated an rpc slot, then the usual mechanism for releasing the write
lock in xprt_release() is defeated.

The problem occurs if the call to xprt_lock_write() initially fails, so
that the rpc_task is put on the xprt->sending wait queue. If the task
exits after being assigned the lock by __xprt_lock_write_func, but
before it has retried the call to xprt_lock_and_alloc_slot(), then
it calls xprt_release() while holding the write lock, but will
immediately exit due to the test for task->tk_rqstp != NULL.

Reported-by: Chris Perl <chris.perl@gmail.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: stable@vger.kernel.org [>= 3.1]

1 files changed, 1 insertions, 2 deletions

diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index b4133bd13915..bfa31714581f 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -972,8 +972,7 @@ static void rpc_async_release(struct work_struct *work)
 
 static void rpc_release_resources_task(struct rpc_task *task)
 {
-        if (task->tk_rqstp)
-                xprt_release(task);
+        xprt_release(task);
         if (task->tk_msg.rpc_cred) {
                 put_rpccred(task->tk_msg.rpc_cred);
                 task->tk_msg.rpc_cred = NULL;