From a93d01f5777e99f24b5b3948e06673ada148337c Mon Sep 17 00:00:00 2001 From: Sowmini Varadhan Date: Thu, 14 Jul 2016 03:51:01 -0700 Subject: [PATCH] RDS: TCP: avoid bad page reference in rds_tcp_listen_data_ready As the existing comments in rds_tcp_listen_data_ready() indicate, it is possible under some race-windows to get to this function with the accept() socket. If that happens, we could run into a sequence whereby thread 1 thread 2 rds_tcp_accept_one() thread sets up new_sock via ->accept(). The sk_user_data is now sock_def_readable data comes in for new_sock, ->sk_data_ready is called, and we land in rds_tcp_listen_data_ready rds_tcp_set_callbacks() takes the sk_callback_lock and sets up sk_user_data to be the cp read_lock sk_callback_lock ready = cp unlock sk_callback_lock page fault on ready In the above sequence, we end up with a panic on a bad page reference when trying to execute (*ready)(). Instead we need to call sock_def_readable() safely, which is what this patch achieves. Acked-by: Santosh Shilimkar Signed-off-by: Sowmini Varadhan Signed-off-by: David S. Miller --- net/rds/tcp.c | 7 +++++++ net/rds/tcp.h | 1 + net/rds/tcp_listen.c | 2 ++ 3 files changed, 10 insertions(+) diff --git a/net/rds/tcp.c b/net/rds/tcp.c index d24f6c142d03..b411bb764f07 100644 --- a/net/rds/tcp.c +++ b/net/rds/tcp.c @@ -551,6 +551,13 @@ static void rds_tcp_kill_sock(struct net *net) } } +void *rds_tcp_listen_sock_def_readable(struct net *net) +{ + struct rds_tcp_net *rtn = net_generic(net, rds_tcp_netid); + + return rtn->rds_tcp_listen_sock->sk->sk_user_data; +} + static int rds_tcp_dev_event(struct notifier_block *this, unsigned long event, void *ptr) { diff --git a/net/rds/tcp.h b/net/rds/tcp.h index 1c3160faa963..9a1cc8906576 100644 --- a/net/rds/tcp.h +++ b/net/rds/tcp.h @@ -70,6 +70,7 @@ void rds_tcp_listen_stop(struct socket *); void rds_tcp_listen_data_ready(struct sock *sk); int rds_tcp_accept_one(struct socket *sock); int rds_tcp_keepalive(struct socket *sock); +void *rds_tcp_listen_sock_def_readable(struct net *net); /* tcp_recv.c */ int rds_tcp_recv_init(void); diff --git a/net/rds/tcp_listen.c b/net/rds/tcp_listen.c index ca975a217a49..73040e319e4b 100644 --- a/net/rds/tcp_listen.c +++ b/net/rds/tcp_listen.c @@ -183,6 +183,8 @@ void rds_tcp_listen_data_ready(struct sock *sk) */ if (sk->sk_state == TCP_LISTEN) rds_tcp_accept_work(sk); + else + ready = rds_tcp_listen_sock_def_readable(sock_net(sk)); out: read_unlock_bh(&sk->sk_callback_lock); -- 2.20.1