linux-kernel - Re: [PATCH] mm/x86: AMD Bulldozer ASLR fix

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Message-ID: <20150329095334.GA4973@pd.tnic>
Date:	Sun, 29 Mar 2015 11:53:34 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Hector Marco-Gisbert <hecmargi@....es>,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jan-Simon <dl9pf@....de>, linux-fsdevel@...r.kernel.org,
	kees Cook <keescook@...omium.org>,
	Ismael Ripoll <iripoll@...ca.upv.es>
Subject: Re: [PATCH] mm/x86: AMD Bulldozer ASLR fix

On Sun, Mar 29, 2015 at 10:51:22AM +0200, Ingo Molnar wrote:
> s/reduces the mmapped file's entropy by 3 bits
> 
> Which does:
> 
>  - a grammar fix
> 
>  - measure it in bits, as later on we are talking about randomness in 
>    bits as well.

Fixed.

> Btw., does this limitation affect both executable and non-executable
> mmap()s?

Only executable mappings.

> Because data mmap()s don't need this I$ related workaround, right? So
> we could relax it for data-mmap()s?

Well, AFAIR, we wanted to keep this as less intrusive as possble. If
we're going to relax this, one way to solve it would be to pass down
@prot from do_mmap_pgoff() and friends to get_unmapped_area() which
would need to touch other arches.

I'm not sure it is worth it...

-- 
Regards/Gruss,
    Boris.

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