netdev - Re: [PATCH net] mptcp: fix use-after-free for ipv6

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Date:   Thu, 06 Feb 2020 11:25:25 +0100 (CET)
From:   David Miller <davem@...emloft.net>
To:     fw@...len.de
Cc:     netdev@...r.kernel.org, cpaasch@...le.com
Subject: Re: [PATCH net] mptcp: fix use-after-free for ipv6

From: Florian Westphal <fw@...len.de>
Date: Thu,  6 Feb 2020 00:39:37 +0100

> Turns out that when we accept a new subflow, the newly created
> inet_sk(tcp_sk)->pinet6 points at the ipv6_pinfo structure of the
> listener socket.
> 
> This wasn't caught by the selftest because it closes the accepted fd
> before the listening one.
> 
> adding a close(listenfd) after accept returns is enough:
>  BUG: KASAN: use-after-free in inet6_getname+0x6ba/0x790
>  Read of size 1 at addr ffff88810e310866 by task mptcp_connect/2518
>  Call Trace:
>   inet6_getname+0x6ba/0x790
>   __sys_getpeername+0x10b/0x250
>   __x64_sys_getpeername+0x6f/0xb0
> 
> also alter test program to exercise this.
> 
> Reported-by: Christoph Paasch <cpaasch@...le.com>
> Signed-off-by: Florian Westphal <fw@...len.de>

Applied, thanks Florian.