From d624d276d1ddacbcb12ad96832ce0c7b82cd25db Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 14 Aug 2017 17:44:43 -0700
Subject: 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: 8fac365f63c8 ("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>
---
net/ipv6/tcp_ipv6.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
(limited to 'net/ipv6/tcp_ipv6.c')
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 2521690d62d6..206210125fd7 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -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;
--
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