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

From: Borislav Petkov <bp@alien8.de>
To: Ingo Molnar <mingo@kernel.org>
Cc: Hector Marco-Gisbert <hecmargi@upv.es>,
	linux-kernel@vger.kernel.org, akpm@linux-foundation.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
	x86@kernel.org, Alexander Viro <viro@zeniv.linux.org.uk>,
	Jan-Simon <dl9pf@gmx.de>,
	linux-fsdevel@vger.kernel.org, kees Cook <keescook@chromium.org>,
	Ismael Ripoll <iripoll@disca.upv.es>
Subject: Re: [PATCH] mm/x86: AMD Bulldozer ASLR fix
Date: Sun, 29 Mar 2015 11:53:34 +0200	[thread overview]
Message-ID: <20150329095334.GA4973@pd.tnic> (raw)
In-Reply-To: <20150329085122.GA25177@gmail.com>

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.
--