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]
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c
index b4133bd..bfa3171 100644
--- a/net/sunrpc/sched.c
+++ b/net/sunrpc/sched.c
@@ -972,8 +972,7 @@
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;
diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c
index bd462a5..33811db 100644
--- a/net/sunrpc/xprt.c
+++ b/net/sunrpc/xprt.c
@@ -1136,10 +1136,18 @@
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)