[PATCH 3.18 140/145] tcp: fix various issues for sockets morphing to listen state

Greg Kroah-Hartman
2017-04-16T10:58:13Z

From: Eric Dumazet <edumazet@google.com>

commit 02b2faaf0af1d85585f6d6980e286d53612acfc2 upstream.

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>

---
net/ipv4/tcp_ipv4.c | 7 +++++--
net/ipv4/tcp_timer.c | 6 ++++--
2 files changed, 9 insertions(+), 4 deletions(-)

--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -271,10 +271,13 @@ 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;
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -207,7 +207,8 @@ void tcp_delack_timer_handler(struct soc

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)) {
@@ -486,7 +487,8 @@ void tcp_write_timer_handler(struct sock
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)) {