Re: [PATCH] ipv4: avoid divide 0 error in tcp_incr_quickack

[David Miller]

From: Chen Weilong <chenweilong@xxxxxxxxxx>
Date: Fri, 31 Oct 2014 22:50:47 +0800

> From: Weilong Chen <chenweilong@xxxxxxxxxx>
> 
> We got a problem like this:
>  [ffff8801c1a05570] machine_kexec at ffffffff81025039
>  [ffff8801c1a055d0] crash_kexec at ffffffff8109b253
>  [ffff8801c1a056a0] oops_end at ffffffff81442aed
>  [ffff8801c1a056d0] die at ffffffff81005603
>  [ffff8801c1a05700] do_trap at ffffffff81442448
>  [ffff8801c1a05760] do_divide_error at ffffffff81002c10
>  [ffff8801c1a05888] tcp_send_dupack at ffffffff81385e44
>  [ffff8801c1a058c8] tcp_validate_incoming at ffffffff813886b5
>  [ffff8801c1a05908] tcp_rcv_state_process at ffffffff8138d0b7
>  [ffff8801c1a05958] tcp_child_process at ffffffff81397255
>  [ffff8801c1a05988] tcp_v4_do_rcv at ffffffff81395a70
>  [ffff8801c1a059d8] tcp_v4_rcv at ffffffff81396fc8
>  [ffff8801c1a05a48] ip_local_deliver_finish at ffffffff813746e9
>  [ffff8801c1a05a78] ip_local_deliver at ffffffff81374a20
>  [ffff8801c1a05aa8] ip_rcv_finish at ffffffff81374389
>  [ffff8801c1a05ad8] ip_rcv at ffffffff81374c78
> There was a wrong ack packet coming during TCP handshake. The socket's state
> was TCP_SYN_RECV, its rcv_mss was not initialize yet. So
> tcp_send_dupack -> tcp_enter_quickack_mode got a divide 0 error.
> This patch add a state check before tcp_enter_quickack_mode.
> 
> Signed-off-by: Weilong Chen <chenweilong@xxxxxxxxxx>

Can you please resubmit this, properly CC:'ing netdev@xxxxxxxxxxxxxxx this
time?

Thank you.
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