| From | Herton Ronaldo Krzesinski <> | Subject | [PATCH 36/74] SUNRPC: Ensure we release the socket write lock if the rpc_task exits early | Date | Thu, 24 Jan 2013 01:26:48 -0200 |
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3.5.7.4 -stable review patch. If anyone has any objections, please let me know.
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From: Trond Myklebust <Trond.Myklebust@netapp.com>
commit 87ed50036b866db2ec2ba16b2a7aec4a2b0b7c39 upstream.
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> Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com> --- net/sunrpc/sched.c | 3 +-- net/sunrpc/xprt.c | 12 ++++++++++-- 2 files changed, 11 insertions(+), 4 deletions(-)
diff --git a/net/sunrpc/sched.c b/net/sunrpc/sched.c index fe2cf2f..85b9235 100644 --- a/net/sunrpc/sched.c +++ b/net/sunrpc/sched.c @@ -953,8 +953,7 @@ 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; diff --git a/net/sunrpc/xprt.c b/net/sunrpc/xprt.c index 2d5b811..6329ff3 100644 --- a/net/sunrpc/xprt.c +++ b/net/sunrpc/xprt.c @@ -1139,10 +1139,18 @@ 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) -- 1.7.9.5
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