tcp: fix more NULL deref after prequeue changes

When I cooked commit c3658e8d0f1 ("tcp: fix possible NULL dereference in
tcp_vX_send_reset()") I missed other spots we could deref a NULL
skb_dst(skb)

Again, if a socket is provided, we do not need skb_dst() to get a
pointer to network namespace : sock_net(sk) is good enough.

Reported-by: Dann Frazier <dann.frazier@canonical.com>
Bisected-by: Dann Frazier <dann.frazier@canonical.com>
Tested-by: Dann Frazier <dann.frazier@canonical.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Fixes: ca777eff51f7 ("tcp: remove dst refcount false sharing for prequeue mode")
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 14 deletions

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index dc495ae2ead0..c277951d783b 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -787,16 +787,16 @@ static const struct tcp_request_sock_ops tcp_request_sock_ipv6_ops = {
         .queue_hash_add =       inet6_csk_reqsk_queue_hash_add,
 };
 
-static void tcp_v6_send_response(struct sk_buff *skb, u32 seq, u32 ack, u32 win,
-                                 u32 tsval, u32 tsecr, int oif,
-                                 struct tcp_md5sig_key *key, int rst, u8 tclass,
-                                 u32 label)
+static void tcp_v6_send_response(struct sock *sk, struct sk_buff *skb, u32 seq,
+                                 u32 ack, u32 win, u32 tsval, u32 tsecr,
+                                 int oif, struct tcp_md5sig_key *key, int rst,
+                                 u8 tclass, u32 label)
 {
         const struct tcphdr *th = tcp_hdr(skb);
         struct tcphdr *t1;
         struct sk_buff *buff;
         struct flowi6 fl6;
-        struct net *net = dev_net(skb_dst(skb)->dev);
+        struct net *net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
         struct sock *ctl_sk = net->ipv6.tcp_sk;
         unsigned int tot_len = sizeof(struct tcphdr);
         struct dst_entry *dst;
@@ -946,7 +946,7 @@ static void tcp_v6_send_reset(struct sock *sk, struct sk_buff *skb)
                           (th->doff << 2);
 
         oif = sk ? sk->sk_bound_dev_if : 0;
-        tcp_v6_send_response(skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);
+        tcp_v6_send_response(sk, skb, seq, ack_seq, 0, 0, 0, oif, key, 1, 0, 0);
 
 #ifdef CONFIG_TCP_MD5SIG
 release_sk1:
@@ -957,13 +957,13 @@ release_sk1:
 #endif
 }
 
-static void tcp_v6_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
-                            u32 win, u32 tsval, u32 tsecr, int oif,
+static void tcp_v6_send_ack(struct sock *sk, struct sk_buff *skb, u32 seq,
+                            u32 ack, u32 win, u32 tsval, u32 tsecr, int oif,
                             struct tcp_md5sig_key *key, u8 tclass,
                             u32 label)
 {
-        tcp_v6_send_response(skb, seq, ack, win, tsval, tsecr, oif, key, 0, tclass,
-                             label);
+        tcp_v6_send_response(sk, skb, seq, ack, win, tsval, tsecr, oif, key, 0,
+                             tclass, label);
 }
 
 static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
@@ -971,7 +971,7 @@ static void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
         struct inet_timewait_sock *tw = inet_twsk(sk);
         struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
 
-        tcp_v6_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
+        tcp_v6_send_ack(sk, skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
                         tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
                         tcp_time_stamp + tcptw->tw_ts_offset,
                         tcptw->tw_ts_recent, tw->tw_bound_dev_if, tcp_twsk_md5_key(tcptw),
@@ -986,10 +986,10 @@ static void tcp_v6_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
         /* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
          * sk->sk_state == TCP_SYN_RECV -> for Fast Open.
          */
-        tcp_v6_send_ack(skb, (sk->sk_state == TCP_LISTEN) ?
+        tcp_v6_send_ack(sk, skb, (sk->sk_state == TCP_LISTEN) ?
                         tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
-                        tcp_rsk(req)->rcv_nxt,
-                        req->rcv_wnd, tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
+                        tcp_rsk(req)->rcv_nxt, req->rcv_wnd,
+                        tcp_time_stamp, req->ts_recent, sk->sk_bound_dev_if,
                         tcp_v6_md5_do_lookup(sk, &ipv6_hdr(skb)->daddr),
                         0, 0);
 }