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authorSowmini Varadhan <sowmini.varadhan@oracle.com>2016-06-04 14:00:00 -0700
committerDavid S. Miller <davem@davemloft.net>2016-06-07 15:10:15 -0700
commit9c79440e2c5e2518879f1599270f64c3ddda3baf (patch)
tree69cbc888d7d91fe1e3c197443f608e35d54a4c30 /net/rds/threads.c
parent0b6f760cff04a7cdfafc3ec6915e91fed0533d8d (diff)
RDS: TCP: fix race windows in send-path quiescence by rds_tcp_accept_one()
The send path needs to be quiesced before resetting callbacks from rds_tcp_accept_one(), and commit eb192840266f ("RDS:TCP: Synchronize rds_tcp_accept_one with rds_send_xmit when resetting t_sock") achieves this using the c_state and RDS_IN_XMIT bit following the pattern used by rds_conn_shutdown(). However this leaves the possibility of a race window as shown in the sequence below take t_conn_lock in rds_tcp_conn_connect send outgoing syn to peer drop t_conn_lock in rds_tcp_conn_connect incoming from peer triggers rds_tcp_accept_one, conn is marked CONNECTING wait for RDS_IN_XMIT to quiesce any rds_send_xmit threads call rds_tcp_reset_callbacks [.. race-window where incoming syn-ack can cause the conn to be marked UP from rds_tcp_state_change ..] lock_sock called from rds_tcp_reset_callbacks, and we set t_sock to null As soon as the conn is marked UP in the race-window above, rds_send_xmit() threads will proceed to rds_tcp_xmit and may encounter a null-pointer deref on the t_sock. Given that rds_tcp_state_change() is invoked in softirq context, whereas rds_tcp_reset_callbacks() is in workq context, and testing for RDS_IN_XMIT after lock_sock could result in a deadlock with tcp_sendmsg, this commit fixes the race by using a new c_state, RDS_TCP_RESETTING, which will prevent a transition to RDS_CONN_UP from rds_tcp_state_change(). 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/threads.c')
-rw-r--r--net/rds/threads.c10
1 files changed, 8 insertions, 2 deletions
diff --git a/net/rds/threads.c b/net/rds/threads.c
index 454aa6d23327..4a323045719b 100644
--- a/net/rds/threads.c
+++ b/net/rds/threads.c
@@ -71,9 +71,9 @@
struct workqueue_struct *rds_wq;
EXPORT_SYMBOL_GPL(rds_wq);
-void rds_connect_complete(struct rds_connection *conn)
+void rds_connect_path_complete(struct rds_connection *conn, int curr)
{
- if (!rds_conn_transition(conn, RDS_CONN_CONNECTING, RDS_CONN_UP)) {
+ if (!rds_conn_transition(conn, curr, RDS_CONN_UP)) {
printk(KERN_WARNING "%s: Cannot transition to state UP, "
"current state is %d\n",
__func__,
@@ -90,6 +90,12 @@ void rds_connect_complete(struct rds_connection *conn)
queue_delayed_work(rds_wq, &conn->c_send_w, 0);
queue_delayed_work(rds_wq, &conn->c_recv_w, 0);
}
+EXPORT_SYMBOL_GPL(rds_connect_path_complete);
+
+void rds_connect_complete(struct rds_connection *conn)
+{
+ rds_connect_path_complete(conn, RDS_CONN_CONNECTING);
+}
EXPORT_SYMBOL_GPL(rds_connect_complete);
/*