From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Kees Cook <keescook@chromium.org>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Rik van Riel <riel@redhat.com>,
Ard Biesheuvel <ard.biesheuvel@linaro.org>,
Daniel Micay <danielmicay@gmail.com>,
Qualys Security Advisory <qsa@qualys.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Will Deacon <will.deacon@arm.com>,
Benjamin Herrenschmidt <benh@kernel.crashing.org>,
Paul Mackerras <paulus@samba.org>,
Michael Ellerman <mpe@ellerman.id.au>,
Martin Schwidefsky <schwidefsky@de.ibm.com>,
Heiko Carstens <heiko.carstens@de.ibm.com>,
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>,
Pratyush Anand <panand@redhat.com>,
James Hogan <james.hogan@imgtec.com>,
Dmitry Safonov <dsafonov@virtuozzo.com>,
Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com>,
Masahiro Yamada <yamada.masahiro@socionext.com>,
linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org,
linux-fsdevel@vger.kernel.org,
kernel-hardening@lists.openwall.com
Subject: Re: [PATCH v2 0/5] Use ELF_ET_DYN_BASE only for PIE
Date: Sat, 24 Jun 2017 10:11:11 +0100 [thread overview]
Message-ID: <20170624091110.GX4902@n2100.armlinux.org.uk> (raw)
In-Reply-To: <1498251600-132458-1-git-send-email-keescook@chromium.org>
On Fri, Jun 23, 2017 at 01:59:55PM -0700, Kees Cook wrote:
> This is v2 (to refresh the 5 patches in -mm) for moving ELF_ET_DYN_BASE
> safely lower. Changes are clarifications in the commit logs (suggested
> by mpe), a compat think-o fix for arm64 (thanks to Ard), and to add
> Rik and mpe's Acks.
>
> Quoting patch 1/5:
>
> The ELF_ET_DYN_BASE position was originally intended to keep loaders
> away from ET_EXEC binaries. (For example, running "/lib/ld-linux.so.2
> /bin/cat" might cause the subsequent load of /bin/cat into where the
> loader had been loaded.) With the advent of PIE (ET_DYN binaries with
> an INTERP Program Header), ELF_ET_DYN_BASE continued to be used since
> the kernel was only looking at ET_DYN. However, since ELF_ET_DYN_BASE
> is traditionally set at the top 1/3rd of the TASK_SIZE, a substantial
> portion of the address space is unused.
With existing kernels on ARM:
00010000-00017000 r-xp 00000000 08:01 270810 /bin/cat
00026000-00027000 r--p 00006000 08:01 270810 /bin/cat
00027000-00028000 rw-p 00007000 08:01 270810 /bin/cat
7f661000-7f679000 r-xp 00000000 08:01 281659 /lib/arm-linux-gnueabihf/ld-2.23.so
7f688000-7f689000 r--p 00017000 08:01 281659 /lib/arm-linux-gnueabihf/ld-2.23.so
7f689000-7f68a000 rw-p 00018000 08:01 281659 /lib/arm-linux-gnueabihf/ld-2.23.so
If the loader is loaded at 4MB, this means the size of an ET_EXEC
program is limited to less than 4MB - and distros aren't yet
building everything as PIE on ARM.
--
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.
next prev parent reply other threads:[~2017-06-24 9:11 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-06-23 20:59 [PATCH v2 0/5] Use ELF_ET_DYN_BASE only for PIE Kees Cook
2017-06-23 20:59 ` [PATCH v2 1/5] binfmt_elf: " Kees Cook
2017-06-24 19:16 ` Kees Cook
2017-06-23 20:59 ` [PATCH v2 2/5] arm: Move ELF_ET_DYN_BASE to 4MB Kees Cook
2017-06-23 20:59 ` [PATCH v2 3/5] arm64: Move ELF_ET_DYN_BASE to 4GB / 4MB Kees Cook
2017-06-23 20:59 ` [PATCH v2 4/5] powerpc: " Kees Cook
2017-06-23 21:00 ` [PATCH v2 5/5] s390: " Kees Cook
2017-06-24 9:11 ` Russell King - ARM Linux [this message]
2017-06-24 13:58 ` [PATCH v2 0/5] Use ELF_ET_DYN_BASE only for PIE Kees Cook
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