netdev - Re: [PATCH net] tcp: do not inherit mc

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Date:   Tue, 09 May 2017 06:23:35 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>, Pray3r <pray3r.z@...il.com>,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH net] tcp: do not inherit mc_list from parent

On Tue, 2017-05-09 at 05:17 -0700, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@...gle.com>
> 
> syzkaller found a way to trigger double frees from ip_mc_drop_socket()
> 
> It turns out that leave a copy of parent mc_list at accept() time,
> which is very bad.
> 
> Very similar to commit 8b485ce69876 ("tcp: do not inherit
> fastopen_req from parent")
> 
> Initial report from Pray3r, completed by Andrey one.
> Thanks a lot to them !
> 
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Reported-by: Pray3r <pray3r.z@...il.com>
> Reported-by: Andrey Konovalov <andreyknvl@...gle.com>
> Tested-by: Andrey Konovalov <andreyknvl@...gle.com>
> ---
> Notes:
>  - day-0 bug.
>  - Not sure if it makes sense for TCP socket to be able to join MC
> group ?


I will send a V2, putting the fix in inet_csk_clone_lock() so that DCCP
is also fixed ;)