SUNRPC: Ensure we release the socket write lock if the rpc_task exits early (87ed5003) · Commits · 戴 / test

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]

net/sunrpc/sched.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -972,7 +972,6 @@ 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);
		if (task->tk_msg.rpc_cred) {
		put_rpccred(task->tk_msg.rpc_cred);

net/sunrpc/xprt.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -1136,10 +1136,18 @@ static void xprt_request_init(struct rpc_task task, struct rpc_xprt xprt)
		void xprt_release(struct rpc_task *task)
		{
		struct rpc_xprt *xprt;
		struct rpc_rqst *req;
		struct rpc_rqst *req = task->tk_rqstp;

		if (!(req = task->tk_rqstp))
		if (req == NULL) {
		if (task->tk_client) {
		rcu_read_lock();
		xprt = rcu_dereference(task->tk_client->cl_xprt);
		if (xprt->snd_task == task)
		xprt_release_write(xprt, task);
		rcu_read_unlock();
		}
		return;
		}

		xprt = req->rq_xprt;
		if (task->tk_ops->rpc_count_stats != NULL)

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