tcp: fix various issues for sockets morphing to listen state

[ Upstream commit 02b2faaf0af1d85585f6d6980e286d53612acfc2 ]

Dmitry Vyukov reported a divide by 0 triggered by syzkaller, exploiting
tcp_disconnect() path that was never really considered and/or used
before syzkaller ;)

I was not able to reproduce the bug, but it seems issues here are the
three possible actions that assumed they would never trigger on a
listener.

1) tcp_write_timer_handler
2) tcp_delack_timer_handler
3) MTU reduction

Only IPv6 MTU reduction was properly testing TCP_CLOSE and TCP_LISTEN
 states from tcp_v6_mtu_reduced()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 9 insertions, 4 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 2259114c7242..5bb809f12ba1 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -269,10 +269,13 @@ EXPORT_SYMBOL(tcp_v4_connect);
  */
 void tcp_v4_mtu_reduced(struct sock *sk)
 {
-        struct dst_entry *dst;
         struct inet_sock *inet = inet_sk(sk);
-        u32 mtu = tcp_sk(sk)->mtu_info;
+        struct dst_entry *dst;
+        u32 mtu;
 
+        if ((1 << sk->sk_state) & (TCPF_LISTEN | TCPF_CLOSE))
+                return;
+        mtu = tcp_sk(sk)->mtu_info;
         dst = inet_csk_update_pmtu(sk, mtu);
         if (!dst)
                 return;
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 3ea1cf804748..b1e65b3b4361 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -249,7 +249,8 @@ void tcp_delack_timer_handler(struct sock *sk)
 
         sk_mem_reclaim_partial(sk);
 
-        if (sk->sk_state == TCP_CLOSE || !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
+        if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
+            !(icsk->icsk_ack.pending & ICSK_ACK_TIMER))
                 goto out;
 
         if (time_after(icsk->icsk_ack.timeout, jiffies)) {
@@ -552,7 +553,8 @@ void tcp_write_timer_handler(struct sock *sk)
         struct inet_connection_sock *icsk = inet_csk(sk);
         int event;
 
-        if (sk->sk_state == TCP_CLOSE || !icsk->icsk_pending)
+        if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) ||
+            !icsk->icsk_pending)
                 goto out;
 
         if (time_after(icsk->icsk_timeout, jiffies)) {