linux-kernel - Re: [PATCH] Fix for binary

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Message-ID: <CANN689HNM+01fXGNijNCgWtoGEGsxBz1Hi4Z+WNYe02EiREuyA@mail.gmail.com>
Date:	Thu, 15 Dec 2011 14:59:39 -0800
From:	Michel Lespinasse <walken@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix for binary_sysctl() memory leak

On Thu, Dec 15, 2011 at 2:44 PM, Andrew Morton
<akpm@...ux-foundation.org> wrote:
> OK.  Please resend with a new changelog?

All right. Will do as a reply to this (I'll add the same explanation
as in my previous email).

> The bug surprises me - it seems that it makes it trivial for userspace
> to cause leaking of mad amounts of kernel memory, which would cause the
> bug to be found and fixed quickly.
>
> Is it a recent regression, or does the bug trigger only in weird
> circumstances, or what?

As far as I can tell, the bug was introduced in v2.6.33-rc1 by commit
26a7034b40ba80f82f64fa251a2cbf49f9971c6a

It's probably not common because people use sysctl mainly at boot
time, and/or don't use the deprecated binary variant of it anymore.
But yes, it is trivial to exploit...

-- 
Michel "Walken" Lespinasse
A program is never fully debugged until the last user dies.
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