inet: fix possible panic in reqsk_queue_unlink()
[ 3897.923145] BUG: unable to handle kernel NULL pointer dereference at
0000000000000080
[ 3897.931025] IP: [<ffffffffa9f27686>] reqsk_timer_handler+0x1a6/0x243
There is a race when reqsk_timer_handler() and tcp_check_req() call
inet_csk_reqsk_queue_unlink() on the same req at the same time.
Before commit fa76ce7328b2 ("inet: get rid of central tcp/dccp listener
timer"), listener spinlock was held and race could not happen.
To solve this bug, we change reqsk_queue_unlink() to not assume req
must be found, and we return a status, to conditionally release a
refcount on the request sock.
This also means tcp_check_req() in non fastopen case might or not
consume req refcount, so tcp_v6_hnd_req() & tcp_v4_hnd_req() have
to properly handle this.
(Same remark for dccp_check_req() and its callers)
inet_csk_reqsk_queue_drop() is now too big to be inlined, as it is
called 4 times in tcp and 3 times in dccp.
Fixes: fa76ce7328b2 ("inet: get rid of central tcp/dccp listener timer")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index 2b4f21d..ccf4c56 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -453,7 +453,8 @@
iph->saddr, iph->daddr);
if (req) {
nsk = dccp_check_req(sk, skb, req);
- reqsk_put(req);
+ if (!nsk)
+ reqsk_put(req);
return nsk;
}
nsk = inet_lookup_established(sock_net(sk), &dccp_hashinfo,
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 9d05510..5165571 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -301,7 +301,8 @@
&iph->daddr, inet6_iif(skb));
if (req) {
nsk = dccp_check_req(sk, skb, req);
- reqsk_put(req);
+ if (!nsk)
+ reqsk_put(req);
return nsk;
}
nsk = __inet6_lookup_established(sock_net(sk), &dccp_hashinfo,
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index 5f56666..30addee 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -186,8 +186,7 @@
if (child == NULL)
goto listen_overflow;
- inet_csk_reqsk_queue_unlink(sk, req);
- inet_csk_reqsk_queue_removed(sk, req);
+ inet_csk_reqsk_queue_drop(sk, req);
inet_csk_reqsk_queue_add(sk, req, child);
out:
return child;