linux-kernel - Re: [x86] copy_from{to}

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Message-ID: <20150821043552.GA29712@nazgul.tnic>
Date:	Fri, 21 Aug 2015 06:35:52 +0200
From:	Borislav Petkov <bp@...e.de>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	yalin wang <yalin.wang2010@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
	x86@...nel.org, open list <linux-kernel@...r.kernel.org>,
	Will Deacon <will.deacon@....com>
Subject: Re: [x86] copy_from{to}_user question

On Thu, Aug 20, 2015 at 11:22:43AM -0700, H. Peter Anvin wrote:
> There is a valid reason to do this, which is that currently
> copy_{to,from}_user() effectively bypass SMAP as they don't verify that
> the kernel pointer is actually a kernel pointer.

Well, we do STAC before we copy but SMAP is checking for supervisor
access to *user* data. But you say "kernel pointers" which is supervisor
data. What am I missing?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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