[PATCH net-next] tcp: take care of SYN_RECV sockets in tcp_v4_send_ack() and tcp_v6_send_response()

[Eric Dumazet]

TCP can send ACK packets on behalf of SYN_RECV sockets.

tcp_v4_send_ack() and tcp_v6_send_response() incorrectly
dereference sk->sk_mark for non TIME_WAIT sockets.

This field is not defined for SYN_RECV sockets.

Using sk_to_full_sk() should get back to the listener socket.

Note that this also provides a socket pointer to sock_net_uid() calls.

Fixes: 00483690552c ("tcp: Add mark for TIMEWAIT sockets")
Signed-off-by: Eric Dumazet <eduma...@google.com>
Cc: Jon Maxwell <jmaxwel...@gmail.com>
---
 net/ipv4/tcp_ipv4.c | 6 ++++--
 net/ipv6/tcp_ipv6.c | 1 +
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 
f059fbd81a84314ae6fef37f600b0cf28bd2ad30..2bb27d5eae78efdff52a741904d7526a234595d8
 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -856,12 +856,14 @@ static void tcp_v4_send_ack(const struct sock *sk,
        if (oif)
                arg.bound_dev_if = oif;
        arg.tos = tos;
-       arg.uid = sock_net_uid(net, sk_fullsock(sk) ? sk : NULL);
        local_bh_disable();
        ctl_sk = this_cpu_read(*net->ipv4.tcp_sk);
-       if (sk)
+       if (sk) {
+               sk = sk_to_full_sk(sk);
                ctl_sk->sk_mark = (sk->sk_state == TCP_TIME_WAIT) ?
                                   inet_twsk(sk)->tw_mark : sk->sk_mark;
+       }
+       arg.uid = sock_net_uid(net, sk_fullsock(sk) ? sk : NULL);
        ip_send_unicast_reply(ctl_sk,
                              skb, &TCP_SKB_CB(skb)->header.h4.opt,
                              ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 
ad7039137a20f9ad8581d9ca01347c67aa8a8433..ea4dd988bc7f9a90e0d95283e10db5a517a59027
 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -884,6 +884,7 @@ static void tcp_v6_send_response(const struct sock *sk, 
struct sk_buff *skb, u32
        }
 
        if (sk) {
+               sk = sk_to_full_sk(sk);
                if (sk->sk_state == TCP_TIME_WAIT) {
                        mark = inet_twsk(sk)->tw_mark;
                        /* autoflowlabel relies on buff->hash */
-- 
2.22.0.rc2.383.gf4fbbf30c2-goog