From 93dc41bdc5c853916610576c6b48a1704959c70d Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 31 Oct 2013 16:14:36 +1100 Subject: [PATCH] SUNRPC: close a rare race in xs_tcp_setup_socket. We have one report of a crash in xs_tcp_setup_socket. The call path to the crash is: xs_tcp_setup_socket -> inet_stream_connect -> lock_sock_nested. The 'sock' passed to that last function is NULL. The only way I can see this happening is a concurrent call to xs_close: xs_close -> xs_reset_transport -> sock_release -> inet_release inet_release sets: sock->sk = NULL; inet_stream_connect calls lock_sock(sock->sk); which gets NULL. All calls to xs_close are protected by XPRT_LOCKED as are most activations of the workqueue which runs xs_tcp_setup_socket. The exception is xs_tcp_schedule_linger_timeout. So presumably the timeout queued by the later fires exactly when some other code runs xs_close(). To protect against this we can move the cancel_delayed_work_sync() call from xs_destory() to xs_close(). As xs_close is never called from the worker scheduled on ->connect_worker, this can never deadlock. Signed-off-by: NeilBrown [Trond: Make it safe to call cancel_delayed_work_sync() on AF_LOCAL sockets] Signed-off-by: Trond Myklebust --- net/sunrpc/xprtsock.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-) diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c index 9deed17fd3e4..a4709bbf8e5e 100644 --- a/net/sunrpc/xprtsock.c +++ b/net/sunrpc/xprtsock.c @@ -835,6 +835,8 @@ static void xs_close(struct rpc_xprt *xprt) dprintk("RPC: xs_close xprt %p\n", xprt); + cancel_delayed_work_sync(&transport->connect_worker); + xs_reset_transport(transport); xprt->reestablish_timeout = 0; @@ -869,12 +871,8 @@ static void xs_local_destroy(struct rpc_xprt *xprt) */ static void xs_destroy(struct rpc_xprt *xprt) { - struct sock_xprt *transport = container_of(xprt, struct sock_xprt, xprt); - dprintk("RPC: xs_destroy xprt %p\n", xprt); - cancel_delayed_work_sync(&transport->connect_worker); - xs_local_destroy(xprt); } @@ -1817,6 +1815,10 @@ static inline void xs_reclassify_socket(int family, struct socket *sock) } #endif +static void xs_dummy_setup_socket(struct work_struct *work) +{ +} + static struct socket *xs_create_sock(struct rpc_xprt *xprt, struct sock_xprt *transport, int family, int type, int protocol) { @@ -2668,6 +2670,9 @@ static struct rpc_xprt *xs_setup_local(struct xprt_create *args) xprt->ops = &xs_local_ops; xprt->timeout = &xs_local_default_timeout; + INIT_DELAYED_WORK(&transport->connect_worker, + xs_dummy_setup_socket); + switch (sun->sun_family) { case AF_LOCAL: if (sun->sun_path[0] != '/') { -- 2.20.1