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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2016-05-02 11:24:51 -0700
committerDavid S. Miller <davem@davemloft.net>2016-05-03 16:03:44 -0400
commiteb192840266fab3e3da644018121eed30153355d (patch)
tree882f8ee60fe758e2e78275cdf00349cce1878000 /net/rds/tcp.c
parent42c8819b8d7245f54d5cfa6c2ec5a436818aeda9 (diff)
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 <sowmini.varadhan@oracle.com> Acked-by: Santosh Shilimkar <santosh.shilimkar@oracle.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/rds/tcp.c')
-rw-r--r--net/rds/tcp.c2
1 files changed, 1 insertions, 1 deletions
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)