tcp: fix possible NULL dereference in tcp_vX_send_reset()

After commit ca777eff51f7 ("tcp: remove dst refcount false sharing for
prequeue mode") we have to relax check against skb dst in
tcp_v[46]_send_reset() if prequeue dropped the dst.

If a socket is provided, a full lookup was done to find this socket,
so the dst test can be skipped.

Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=88191
Reported-by: Jaša Bartelj <jasa.bartelj@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Daniel Borkmann <dborkman@redhat.com>
Fixes: ca777eff51f7 ("tcp: remove dst refcount false sharing for prequeue mode")
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 9c7d7621466b1241f404a5ca11de809dcff2d02a..147be202429064d03b34405dba575c8d002b267c 100644 (file)
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -598,7 +598,10 @@ static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb)
        if (th->rst)
                return;
 
-       if (skb_rtable(skb)->rt_type != RTN_LOCAL)
+       /* If sk not NULL, it means we did a successful lookup and incoming
+        * route had to be correct. prequeue might have dropped our dst.
+        */
+       if (!sk && skb_rtable(skb)->rt_type != RTN_LOCAL)
                return;
 
        /* Swap the send and the receive. */

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ace29b60813cf8a1d7182ad2262cbcbd21810fa7..dc495ae2ead05aca0190bcab8c2d95b58beb2ac9 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -903,7 +903,10 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb)
        if (th->rst)
                return;
 
-       if (!ipv6_unicast_destination(skb))
+       /* If sk not NULL, it means we did a successful lookup and incoming
+        * route had to be correct. prequeue might have dropped our dst.
+        */
+       if (!sk && !ipv6_unicast_destination(skb))
                return;
 
 #ifdef CONFIG_TCP_MD5SIG