linux-kernel - Re: net: socket: NULL ptr deref in sendmsg

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Date:	Sat, 26 Jul 2014 00:15:53 +0200
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	Andrey Ryabinin <a.ryabinin@...sung.com>,
	"David S. Miller" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	Eric Dumazet <edumazet@...gle.com>
Subject: Re: net: socket: NULL ptr deref in sendmsg

On Fr, 2014-07-25 at 16:52 -0400, Sasha Levin wrote:
> On 07/25/2014 11:23 AM, Andrey Ryabinin wrote:
> > After this report there was no usual "Unable to handle kernel NULL pointer dereference"
> > and this gave me a clue that address 0 is mapped and contains valid socket address structure in it.
> 
> Interesting. Does it mean that all network protocols that check it for being NULL instead of checking
> the length are incorrect?

I would not like to go down this route and keep msg->msg_namelen and
msg->msg_name in sync after verify_iovec.

> (such as:)
> 
>         if (msg->msg_name) {
>                 DECLARE_SOCKADDR(struct sockaddr_can *, addr, msg->msg_name);
> 
>                 [...]
> 

Thanks,
Hannes

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