linux-kernel - Re: [PATCH 2/2] x86: ia32_signal: remove unnecessary padding

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Message-ID: <491B1C7C.5000906@zytor.com>
Date:	Wed, 12 Nov 2008 10:12:12 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
CC:	Mikael Pettersson <mikpe@...uu.se>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] x86: ia32_signal: remove unnecessary padding

Hiroshi Shimamoto wrote:
> H. Peter Anvin wrote:
>> Mikael Pettersson wrote:
>>> It does cause each signal delivery to leak 2 uninitialised
>>> kernel bytes to the end of retcode[], which seems unnecessary.
>> Not just unnecessary, it is a huge no-no for security.
> 
> Am I missing important thing?
> The frame->retcode is 8 bytes and packed structure with padding
> is 10 bytes each, and the code is copied to user stack 8 bytes only.
> 
> err |= __copy_to_user(frame->retcode, &code, 8);
> 
> I don't think the behavior is changed.
> 

Ah, nevermind, then.  Then it fine, obviously.

	-hpa
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