Commit a93d01f5 authored Jul 14, 2016 by Sowmini Varadhan Committed by David S. Miller Jul 15, 2016

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 <santosh.shilimkar@oracle.com>
Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent caeccd51

net/rds/tcp.c

+7 −0

Original line number	Diff line number	Diff line
		@@ -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)
		{

net/rds/tcp.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -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);

net/rds/tcp_listen.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -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);

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