linux-kernel - Re: mpol_to

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Message-ID: <1349742791.6336.11.camel@deadeye.wl.decadent.org.uk>
Date:	Tue, 09 Oct 2012 01:33:11 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	Dave Jones <davej@...hat.com>
Cc:	Linux Kernel <linux-kernel@...r.kernel.org>, linux-mm@...ck.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: mpol_to_str revisited.

On Mon, 2012-10-08 at 11:09 -0400, Dave Jones wrote:
> Last month I sent in 80de7c3138ee9fd86a98696fd2cf7ad89b995d0a to remove
> a user triggerable BUG in mempolicy.
> 
> Ben Hutchings pointed out to me that my change introduced a potential leak
> of stack contents to userspace, because none of the callers check the return value.
> 
> This patch adds the missing return checking, and also clears the buffer beforehand.
>
> Reported-by: Ben Hutchings <bhutchings@...arflare.com>

I was wearing my other hat at the time (ben@...adent.org.uk).

> Cc: stable@...nel.org
> Signed-off-by: Dave Jones <davej@...hat.com>
> 
> --- 
> unanswered question: why are the buffer sizes here different ? which is correct?
[...]

Further question: why even use an intermediate buffer on the stack?
Both callers want to write the result to a seq_file.  Should mpol_str()
then be replaced with a seq_mpol()?

Ben.

-- 
Ben Hutchings
Who are all these weirdos? - David Bowie, about L-Space IRC channel #afp

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