netdev - Re:Re: [PATCH net] net: Fix one possible memleak in ip_setup

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Date:   Wed, 18 Apr 2018 09:33:49 +0800 (CST)
From:   "Gao Feng" <gfree.wind@....163.com>
To:     "Eric Dumazet" <eric.dumazet@...il.com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re:Re: [PATCH net] net: Fix one possible memleak in ip_setup_cork

At 2018-04-17 05:18:25, "Eric Dumazet" <eric.dumazet@...il.com> wrote:
>
>
>On 04/16/2018 09:58 AM, David Miller wrote:
>> From: gfree.wind@....163.com
>> Date: Mon, 16 Apr 2018 10:16:45 +0800
>> 
>>> From: Gao Feng <gfree.wind@....163.com>
>>>
>>> It would allocate memory in this function when the cork->opt is NULL. But
>>> the memory isn't freed if failed in the latter rt check, and return error
>>> directly. It causes the memleak if its caller is ip_make_skb which also
>>> doesn't free the cork->opt when meet a error.
>>>
>>> Now move the rt check ahead to avoid the memleak.
>>>
>>> Signed-off-by: Gao Feng <gfree.wind@....163.com>
>> 
>> Looks good, applied and queued up for -stable.
>> 
>> I guess in the other code paths, ip_flush_pending_frames() or similar
>> would clean up the in-sock cork information.
>> 
>
>I am not sure ip_make_skb() can be called with a NULL rt.
>
>Patch makes no harm, but does not seem to fix a bug.
>

Thanks Eric.

I just look up current all callers of ip_make_skb and ip_append_data, they check
if the rt is valid ahead. So current codes won't pass one NULL rt to ip_setup_cork indeed.

Then this patch is just as an enhancement, not a fix. 
As the programming rule, the function should free the mem which is allocated by itself when
it failed.

Best Regards
Feng