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| author | Eric Dumazet <edumazet@google.com> | 2017-08-03 08:10:46 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2017-08-03 18:34:51 +0200 |
| commit | 2dda640040876cd8ae646408b69eea40c24f9ae9 (patch) | |
| tree | 416cddf4e94f0bc5e133492aebe11bef8c417465 /net | |
| parent | Merge tag 'batadv-net-for-davem-20170802' of git://git.open-mesh.org/linux-merge (diff) | |
| download | linux-2dda640040876cd8ae646408b69eea40c24f9ae9.tar.xz linux-2dda640040876cd8ae646408b69eea40c24f9ae9.zip | |
net: fix keepalive code vs TCP_FASTOPEN_CONNECT
syzkaller was able to trigger a divide by 0 in TCP stack [1]
Issue here is that keepalive timer needs to be updated to not attempt
to send a probe if the connection setup was deferred using
TCP_FASTOPEN_CONNECT socket option added in linux-4.11
[1]
divide error: 0000 [#1] SMP
CPU: 18 PID: 0 Comm: swapper/18 Not tainted
task: ffff986f62f4b040 ti: ffff986f62fa2000 task.ti: ffff986f62fa2000
RIP: 0010:[<ffffffff8409cc0d>] [<ffffffff8409cc0d>] __tcp_select_window+0x8d/0x160
Call Trace:
<IRQ>
[<ffffffff8409d951>] tcp_transmit_skb+0x11/0x20
[<ffffffff8409da21>] tcp_xmit_probe_skb+0xc1/0xe0
[<ffffffff840a0ee8>] tcp_write_wakeup+0x68/0x160
[<ffffffff840a151b>] tcp_keepalive_timer+0x17b/0x230
[<ffffffff83b3f799>] call_timer_fn+0x39/0xf0
[<ffffffff83b40797>] run_timer_softirq+0x1d7/0x280
[<ffffffff83a04ddb>] __do_softirq+0xcb/0x257
[<ffffffff83ae03ac>] irq_exit+0x9c/0xb0
[<ffffffff83a04c1a>] smp_apic_timer_interrupt+0x6a/0x80
[<ffffffff83a03eaf>] apic_timer_interrupt+0x7f/0x90
<EOI>
[<ffffffff83fed2ea>] ? cpuidle_enter_state+0x13a/0x3b0
[<ffffffff83fed2cd>] ? cpuidle_enter_state+0x11d/0x3b0
Tested:
Following packetdrill no longer crashes the kernel
`echo 0 >/proc/sys/net/ipv4/tcp_timestamps`
// Cache warmup: send a Fast Open cookie request
0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
+0 setsockopt(3, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
+0 connect(3, ..., ...) = -1 EINPROGRESS (Operation is now in progress)
+0 > S 0:0(0) <mss 1460,nop,nop,sackOK,nop,wscale 8,FO,nop,nop>
+.01 < S. 123:123(0) ack 1 win 14600 <mss 1460,nop,nop,sackOK,nop,wscale 6,FO abcd1234,nop,nop>
+0 > . 1:1(0) ack 1
+0 close(3) = 0
+0 > F. 1:1(0) ack 1
+0 < F. 1:1(0) ack 2 win 92
+0 > . 2:2(0) ack 2
+0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 4
+0 fcntl(4, F_SETFL, O_RDWR|O_NONBLOCK) = 0
+0 setsockopt(4, SOL_TCP, TCP_FASTOPEN_CONNECT, [1], 4) = 0
+0 setsockopt(4, SOL_SOCKET, SO_KEEPALIVE, [1], 4) = 0
+.01 connect(4, ..., ...) = 0
+0 setsockopt(4, SOL_TCP, TCP_KEEPIDLE, [5], 4) = 0
+10 close(4) = 0
`echo 1 >/proc/sys/net/ipv4/tcp_timestamps`
Fixes: 19f6d3f3c842 ("net/tcp-fastopen: Add new API support")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Wei Wang <weiwan@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/tcp_timer.c | 3 |
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c index c0feeeef962a..e906014890b6 100644 --- a/net/ipv4/tcp_timer.c +++ b/net/ipv4/tcp_timer.c @@ -652,7 +652,8 @@ static void tcp_keepalive_timer (unsigned long data) goto death; } - if (!sock_flag(sk, SOCK_KEEPOPEN) || sk->sk_state == TCP_CLOSE) + if (!sock_flag(sk, SOCK_KEEPOPEN) || + ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) goto out; elapsed = keepalive_time_when(tp); |