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

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Message-ID: <20150822090519.GA2812@nazgul.tnic>
Date:	Sat, 22 Aug 2015 11:05:19 +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 Fri, Aug 21, 2015 at 02:06:16PM -0700, H. Peter Anvin wrote:
> What I'm saying is that we do do STAC, which *disables* SMAP.  We have
> to do that because one pointer is known to be a user space pointer.
> 
> However, we currently don't verify that the *other* pointer is kernel
> space, which it is supposed to be (if not, we should be using
> copy_in_user).  We have to do this manually since we have to STAC which
> means SMAP doesn't do anything at all.  I believe it would be a good
> idea to add such checks (and they would even benefit non-SMAP hardware.)

Ah, ok, so we're on the same page.

And yep, Linus gave the probe_kernel_read() suggestion in another mail.

-- 
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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