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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]
This commit is contained in:
Trond Myklebust 2013-01-07 14:30:46 -05:00
parent d287b8750e
commit 87ed50036b
2 changed files with 11 additions and 4 deletions
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3
net/sunrpc/sched.c
View File

@ -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;

12
net/sunrpc/xprt.c
View File

@ -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)