Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit d624d276 authored Aug 14, 2017 by Eric Dumazet Committed by David S. Miller Aug 14, 2017

tcp: fix possible deadlock in TCP stack vs BPF filter



Filtering the ACK packet was not put at the right place.

At this place, we already allocated a child and put it
into accept queue.

We absolutely need to call tcp_child_process() to release
its spinlock, or we will deadlock at accept() or close() time.

Found by syzkaller team (Thanks a lot !)

Fixes: 8fac365f ("tcp: Add a tcp_filter hook before handle ack packet")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Chenbo Feng <fengc@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent 7749d4ff

net/ipv4/tcp_ipv4.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1722,6 +1722,8 @@ int tcp_v4_rcv(struct sk_buff *skb)
	*/		*/
	sock_hold(sk);		sock_hold(sk);
	refcounted = true;		refcounted = true;
			if (tcp_filter(sk, skb))
			goto discard_and_relse;
	nsk = tcp_check_req(sk, skb, req, false);		nsk = tcp_check_req(sk, skb, req, false);
	if (!nsk) {		if (!nsk) {
	reqsk_put(req);		reqsk_put(req);
	@@ -1729,8 +1731,6 @@ int tcp_v4_rcv(struct sk_buff *skb)
	}		}
	if (nsk == sk) {		if (nsk == sk) {
	reqsk_put(req);		reqsk_put(req);
	} else if (tcp_filter(sk, skb)) {
	goto discard_and_relse;
	} else if (tcp_child_process(sk, nsk, skb)) {		} else if (tcp_child_process(sk, nsk, skb)) {
	tcp_v4_send_reset(nsk, skb);		tcp_v4_send_reset(nsk, skb);
	goto discard_and_relse;		goto discard_and_relse;

net/ipv6/tcp_ipv6.c

+2 −2

Original line number	Original line	Diff line number	Diff line
	@@ -1456,6 +1456,8 @@ static int tcp_v6_rcv(struct sk_buff *skb)
	}		}
	sock_hold(sk);		sock_hold(sk);
	refcounted = true;		refcounted = true;
			if (tcp_filter(sk, skb))
			goto discard_and_relse;
	nsk = tcp_check_req(sk, skb, req, false);		nsk = tcp_check_req(sk, skb, req, false);
	if (!nsk) {		if (!nsk) {
	reqsk_put(req);		reqsk_put(req);
	@@ -1464,8 +1466,6 @@ static int tcp_v6_rcv(struct sk_buff *skb)
	if (nsk == sk) {		if (nsk == sk) {
	reqsk_put(req);		reqsk_put(req);
	tcp_v6_restore_cb(skb);		tcp_v6_restore_cb(skb);
	} else if (tcp_filter(sk, skb)) {
	goto discard_and_relse;
	} else if (tcp_child_process(sk, nsk, skb)) {		} else if (tcp_child_process(sk, nsk, skb)) {
	tcp_v6_send_reset(nsk, skb);		tcp_v6_send_reset(nsk, skb);
	goto discard_and_relse;		goto discard_and_relse;