[PATCH] SUNRPC: fix race in in-kernel RPC portmapper client

When submitting a request to a fast portmapper (such as the local rpcbind
daemon), the request can complete before the parent task is even queued up on
xprt->binding.  Fix this by queuing before submitting the rpcbind request.

Test plan:
Connectathon locking test with UDP.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/net/sunrpc/pmap_clnt.c b/net/sunrpc/pmap_clnt.c
index 919d5ba..e52afab 100644 (file)
--- a/net/sunrpc/pmap_clnt.c
+++ b/net/sunrpc/pmap_clnt.c
@@ -101,11 +101,13 @@ void rpc_getport(struct rpc_task *task)
        /* Autobind on cloned rpc clients is discouraged */
        BUG_ON(clnt->cl_parent != clnt);
 
-       if (xprt_test_and_set_binding(xprt)) {
-               task->tk_status = -EACCES;      /* tell caller to check again */
-               rpc_sleep_on(&xprt->binding, task, NULL, NULL);
-               return;
-       }
+       /* Put self on queue before sending rpcbind request, in case
+        * pmap_getport_done completes before we return from rpc_run_task */
+       rpc_sleep_on(&xprt->binding, task, NULL, NULL);
+
+       status = -EACCES;               /* tell caller to check again */
+       if (xprt_test_and_set_binding(xprt))
+               goto bailout_nofree;
 
        /* Someone else may have bound if we slept */
        status = 0;
@@ -134,8 +136,6 @@ void rpc_getport(struct rpc_task *task)
                goto bailout;
        rpc_release_task(child);
 
-       rpc_sleep_on(&xprt->binding, task, NULL, NULL);
-
        task->tk_xprt->stat.bind_count++;
        return;