netdev - Re: [PATCH net] net: diag: Don't double-free TCP_NEW_SYN_RECV sockets in tcp

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Date:   Mon, 9 Jul 2018 08:59:15 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Lorenzo Colitti <lorenzo@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Cc:     David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
        Alistair Strachan <astrachan@...gle.com>,
        Subash Abhinov Kasiviswanathan <subashab@...eaurora.org>
Subject: Re: [PATCH net] net: diag: Don't double-free TCP_NEW_SYN_RECV sockets
 in tcp_abort

On 7/8/18 10:53 PM, Lorenzo Colitti wrote:
> On Sat, Jul 7, 2018 at 10:29 PM Eric Dumazet <eric.dumazet@...il.com> wrote:
>>>> Tested: passes Android sock_diag_test.py, which exercises this codepath
>>>
>>> If this Android test case exercises this path, why didn't it trigger
>>> the double free and thus cause this bug to be found much sooner?
>>>
>>> Just curious.
>>
>> Presumably android has not backported yet the refcount_t stuff in their kernels.
> 
> That's correct. We only started seeing this on 4.14, which is not yet
> in the field.

Prior to 4.12 syn-recv sockets did not show up in the list, so it could
not be closed through the diag API. I did not chase it to a specific
commit between 4.11 (no syn-recv in 'ss -ta') and 4.12 (syn-recv shows
up in 'ss -ta').