linux-kernel - Re: [PATCH] netlink: fix (theoretical) overrun in message iteration

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Message-ID: <19f34abd0812210646i70340ac1xe5489f5518484859@mail.gmail.com>
Date:	Sun, 21 Dec 2008 15:46:39 +0100
From:	"Vegard Nossum" <vegard.nossum@...il.com>
To:	"David S. Miller" <davem@...emloft.net>
Cc:	"Thomas Graf" <tgraf@...g.ch>, "Eugene Teo" <eugeneteo@...nel.sg>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Al Viro" <viro@...iv.linux.org.uk>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] netlink: fix (theoretical) overrun in message iteration

On Sun, Dec 21, 2008 at 3:44 PM, Vegard Nossum <vegard.nossum@...il.com> wrote:
> On Sun, Dec 21, 2008 at 2:42 PM, Vegard Nossum <vegard.nossum@...il.com> wrote:
>> From bb805d89e84ddb11c9bb58afcfd9a6b37bbe5a9b Mon Sep 17 00:00:00 2001
>> From: Vegard Nossum <vegard.nossum@...il.com>
>> Date: Sun, 21 Dec 2008 14:20:49 +0100
>> Subject: [PATCH] netlink: fix (theoretical) overrun in message iteration
>>
>> See commit 1045b03e07d85f3545118510a587035536030c1c for a detailed
>> explanation of why this patch is necessary.
>>
>> In short, nlmsg_next() can make "remaining" go negative, and the
>> remaining >= sizeof(...) comparison will promote "remaining" to an
>> unsigned type, which means that the expression will evaluate to
>> true for negative numbers, even though it was not intended.
>>
>> I put "theoretical" in the title because I have no evidence that
>> this can actually happen, but I suspect that a crafted netlink
>> packet can trigger some badness.
>
> nlmsg

Oops. I meant to say that nlmsg_for_each_msg() has no users at all,
which means that the change is all the more "theoretical" :-)


Vegard

-- 
"The animistic metaphor of the bug that maliciously sneaked in while
the programmer was not looking is intellectually dishonest as it
disguises that the error is the programmer's own creation."
	-- E. W. Dijkstra, EWD1036
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