From eb192840266fab3e3da644018121eed30153355d Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Mon, 2 May 2016 11:24:51 -0700 Subject: RDS:TCP: Synchronize rds_tcp_accept_one with rds_send_xmit when resetting t_sock There is a race condition between rds_send_xmit -> rds_tcp_xmit and the code that deals with resolution of duelling syns added by commit 241b271952eb ("RDS-TCP: Reset tcp callbacks if re-using an outgoing socket in rds_tcp_accept_one()"). Specifically, we may end up derefencing a null pointer in rds_send_xmit if we have the interleaving sequence: rds_tcp_accept_one rds_send_xmit conn is RDS_CONN_UP, so invoke rds_tcp_xmit tc = conn->c_transport_data rds_tcp_restore_callbacks /* reset t_sock */ null ptr deref from tc->t_sock The race condition can be avoided without adding the overhead of additional locking in the xmit path: have rds_tcp_accept_one wait for rds_tcp_xmit threads to complete before resetting callbacks. The synchronization can be done in the same manner as rds_conn_shutdown(). First set the rds_conn_state to something other than RDS_CONN_UP (so that new threads cannot get into rds_tcp_xmit()), then wait for RDS_IN_XMIT to be cleared in the conn->c_flags indicating that any threads in rds_tcp_xmit are done. Fixes: 241b271952eb ("RDS-TCP: Reset tcp callbacks if re-using an outgoing socket in rds_tcp_accept_one()") Signed-off-by: Sowmini Varadhan Acked-by: Santosh Shilimkar Signed-off-by: David S. Miller --- net/rds/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'net/rds/tcp.c') diff --git a/net/rds/tcp.c b/net/rds/tcp.c index 61ed2a8764ba..9134544941c2 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -127,7 +127,7 @@ void rds_tcp_restore_callbacks(struct socket *sock, /* * This is the only path that sets tc->t_sock. Send and receive trust that - * it is set. The RDS_CONN_CONNECTED bit protects those paths from being + * it is set. The RDS_CONN_UP bit protects those paths from being * called while it isn't set. */ void rds_tcp_set_callbacks(struct socket *sock, struct rds_connection *conn) -- cgit v1.2.3