netdev - Re: [PATCH net v2] ppp: reject claimed-as-LCP but actually malformed packets

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Message-ID: <e572a9447628fc6b6ff511df30d923176e664fec.camel@redhat.com>
Date: Thu, 11 Jul 2024 10:41:45 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Simon Horman <horms@...nel.org>, Dmitry Antipov <dmantipov@...dex.ru>
Cc: "David S. Miller" <davem@...emloft.net>, "Ricardo B. Marliere"
 <ricardo@...liere.net>, Eric Dumazet <edumazet@...gle.com>, 
 linux-ppp@...r.kernel.org, netdev@...r.kernel.org,
 lvc-project@...uxtesting.org, 
 syzbot+ec0723ba9605678b14bf@...kaller.appspotmail.com, Guillaume Nault
 <gnault@...hat.com>, Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH net v2] ppp: reject claimed-as-LCP but actually
 malformed packets

On Tue, 2024-07-09 at 09:30 +0100, Simon Horman wrote:
> + Guillaume, Jakub
> 
> On Mon, Jul 08, 2024 at 02:56:15PM +0300, Dmitry Antipov wrote:
> > Since 'ppp_async_encode()' assumes valid LCP packets (with code
> > from 1 to 7 inclusive), add 'ppp_check_packet()' to ensure that
> > LCP packet has an actual body beyond PPP_LCP header bytes, and
> > reject claimed-as-LCP but actually malformed data otherwise.
> > 
> > Reported-by: syzbot+ec0723ba9605678b14bf@...kaller.appspotmail.com
> > Closes: https://syzkaller.appspot.com/bug?extid=ec0723ba9605678b14bf
> > Fixes: 44073187990d ("ppp: ensure minimum packet size in ppp_write()")
> 
> Sorry for not noticing this earlier.
> 
> I think that the cited commit is not where this problem was introduced.
> What that commit does is to introduce a length check.
> And what this patch does is to add another, more specific length check.
> But the problem fixed by this patch existed before the cited commit.
> 
> I expect that, like the cited commit, this patch:
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")

No need to resend, I'll update the tag while applying the patch.

Thanks!

Paolo