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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: 8fac365f63 ("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>
This commit is contained in:
Eric Dumazet 2017-08-14 17:44:43 -07:00 committed by David S. Miller
parent 7749d4ff88
commit d624d276d1
2 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
net/ipv4/tcp_ipv4.c
View File

@ -1722,6 +1722,8 @@ process:
*/
sock_hold(sk);
refcounted = true;
if (tcp_filter(sk, skb))
goto discard_and_relse;
nsk = tcp_check_req(sk, skb, req, false);
if (!nsk) {
reqsk_put(req);
@ -1729,8 +1731,6 @@ process:
}
if (nsk == sk) {
reqsk_put(req);
} else if (tcp_filter(sk, skb)) {
goto discard_and_relse;
} else if (tcp_child_process(sk, nsk, skb)) {
tcp_v4_send_reset(nsk, skb);
goto discard_and_relse;

4
net/ipv6/tcp_ipv6.c
View File

@ -1456,6 +1456,8 @@ process:
}
sock_hold(sk);
refcounted = true;
if (tcp_filter(sk, skb))
goto discard_and_relse;
nsk = tcp_check_req(sk, skb, req, false);
if (!nsk) {
reqsk_put(req);
@ -1464,8 +1466,6 @@ process:
if (nsk == sk) {
reqsk_put(req);
tcp_v6_restore_cb(skb);
} else if (tcp_filter(sk, skb)) {
goto discard_and_relse;
} else if (tcp_child_process(sk, nsk, skb)) {
tcp_v6_send_reset(nsk, skb);
goto discard_and_relse;