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authorEric Dumazet <edumazet@google.com>2017-08-02 23:10:46 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2017-08-12 19:34:26 -0700
commit963f8fb6b8e24944551a2777452edfc88064b481 (patch)
treeb963e98a630c0dbf1c105f5d03a26600cca596eb /net
parent4fe3624211f7860b5d7b83fa04d71e85755a9244 (diff)
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net: fix keepalive code vs TCP_FASTOPEN_CONNECT
[ Upstream commit 2dda640040876cd8ae646408b69eea40c24f9ae9 ] 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp_timer.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 14672543cf0b..0733ea7e17cd 100644
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -654,7 +654,8 @@ 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);