netdev - Re: [syzbot] [mptcp?] general protection fault in proc

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Message-ID: <163dbb5c-124c-4942-9b97-542ea97faa2a@kernel.org>
Date: Sun, 5 Jan 2025 18:03:36 +0100
From: Matthieu Baerts <matttbe@...nel.org>
To: Eric Dumazet <edumazet@...gle.com>, Al Viro <viro@...iv.linux.org.uk>
Cc: davem@...emloft.net, geliang@...nel.org, horms@...nel.org,
 kuba@...nel.org, linux-kernel@...r.kernel.org, martineau@...nel.org,
 mptcp@...ts.linux.dev, netdev@...r.kernel.org, pabeni@...hat.com,
 syzkaller-bugs@...glegroups.com,
 syzbot <syzbot+e364f774c6f57f2c86d1@...kaller.appspotmail.com>
Subject: Re: [syzbot] [mptcp?] general protection fault in proc_scheduler

Hi Eric,

On 05/01/2025 17:52, Eric Dumazet wrote:
> On Sun, Jan 5, 2025 at 12:29 PM Al Viro <viro@...iv.linux.org.uk> wrote:
>>
>> On Sun, Jan 05, 2025 at 09:32:36AM +0100, Eric Dumazet wrote:
>>
>>> According to grep, we have many other places directly reading
>>> current->nsproxy->net_ns
>>> For instance in net/sctp/sysctl.c
>>> Should we change them all ?
>>
>> Depends - do you want their contents match the netns of opener (as,
>> AFAICS, for ipv4 sysctls) or that of the reader?
> 
> I am only worried that a malicious user could crash the host with
> current kernels,
> not about this MPTP crash, but all unaware users of current->nsproxy
> in sysctl handlers.
> 
> Back to MPTCP :
> 
> Using the convention used in other mptcp sysctls like (enabled,
> add_addr_timeout,
> checksum_enabled, allow_join_initial_addr_port...) is better for consistency.

Indeed, I can do the modifications to stop using current->nsproxy in
MPTCP. I can do the same in SCTP.

Do you plan to send your patch modifying proc_sysctl.c? It is just to
know if I should mark my patches as fixes, and split them to ease the
backports -- each helper using current->nsproxy has been introduced in
different commits -- or if I can send them to net-next instead.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.