From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michael Ellerman <mpe@ellerman.id.au>
Subject: Re: [PATCH 4/5] mm: split ET_DYN ASLR from mmap ASLR
Date: Wed, 04 Mar 2015 15:16:41 +1100
Message-ID: <1425442601.9084.9.camel@ellerman.id.au>
References: <1425341988-1599-1-git-send-email-keescook@chromium.org>
	 <1425341988-1599-5-git-send-email-keescook@chromium.org>
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Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	Russell King <linux@arm.linux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	Ralf Baechle <ralf@linux-mips.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linux390@de.ibm.com, x86@kernel.org,
	Alexander Viro <viro@zeniv.linux.org.uk>,
	Oleg Nesterov <oleg@redhat.com>,
	Andy Lutomirski <luto@amacapital.net>,
	"David A. Long" <dave.long@linaro.org>,
	Andrey Ryabinin <a.ryabinin@samsung.com>,
	Arun Chandran <achandran@mvista.com>,
	Yann Droneaud <ydroneaud@opteya.com>,
	Min-Hua Chen <orca.chen@gmail.com>,
	Paul Burton <paul.burton@imgtec.com>,
	Alex Smith <alex@alex-smith.me.uk>,
	Markos Chandras <markos.chandras@imgtec.com>,
	Jeff Bailey <jeffbailey@g
To: Kees Cook <keescook@chromium.org>
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On Mon, 2015-03-02 at 16:19 -0800, Kees Cook wrote:
> This fixes the "offset2lib" weakness in ASLR for arm, arm64, mips,
> powerpc, and x86. The problem is that if there is a leak of ASLR from
> the executable (ET_DYN), it means a leak of shared library offset as
> well (mmap), and vice versa. Further details and a PoC of this attack
> are available here:
> http://cybersecurity.upv.es/attacks/offset2lib/offset2lib.html
> 
> With this patch, a PIE linked executable (ET_DYN) has its own ASLR region:
> 
> $ ./show_mmaps_pie
> 54859ccd6000-54859ccd7000 r-xp  ...  /tmp/show_mmaps_pie
> 54859ced6000-54859ced7000 r--p  ...  /tmp/show_mmaps_pie
> 54859ced7000-54859ced8000 rw-p  ...  /tmp/show_mmaps_pie

Just to be clear, it's the fact that the above vmas are in a different
address range to those below that shows the patch is working, right?

> 7f75be764000-7f75be91f000 r-xp  ...  /lib/x86_64-linux-gnu/libc.so.6
> 7f75be91f000-7f75beb1f000 ---p  ...  /lib/x86_64-linux-gnu/libc.so.6


On powerpc I'm seeing:

# /bin/dash
# cat /proc/$$/maps
524e0000-52510000 r-xp 00000000 08:03 129814                             /bin/dash
52510000-52520000 rw-p 00020000 08:03 129814                             /bin/dash
10034f20000-10034f50000 rw-p 00000000 00:00 0                            [heap]
3fffaeaf0000-3fffaeca0000 r-xp 00000000 08:03 13529                      /lib/powerpc64le-linux-gnu/libc-2.19.so
3fffaeca0000-3fffaecb0000 rw-p 001a0000 08:03 13529                      /lib/powerpc64le-linux-gnu/libc-2.19.so
3fffaecc0000-3fffaecd0000 rw-p 00000000 00:00 0 
3fffaecd0000-3fffaecf0000 r-xp 00000000 00:00 0                          [vdso]
3fffaecf0000-3fffaed20000 r-xp 00000000 08:03 13539                      /lib/powerpc64le-linux-gnu/ld-2.19.so
3fffaed20000-3fffaed30000 rw-p 00020000 08:03 13539                      /lib/powerpc64le-linux-gnu/ld-2.19.so
3fffc7070000-3fffc70a0000 rw-p 00000000 00:00 0                          [stack]


Whereas previously the /bin/dash vmas were up at 3fff..

So looks good to me for powerpc.

Acked-by: Michael Ellerman <mpe@ellerman.id.au>

cheers