Date: Wed, 21 Jun 2017 14:24:26 -0400 From: Rik van Riel <riel@...hat.com> To: Kees Cook <keescook@...omium.org>, Andrew Morton <akpm@...ux-foundation.org> Cc: Daniel Micay <danielmicay@...il.com>, Qualys Security Advisory <qsa@...lys.com>, 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>, Dmitry Safonov <dsafonov@...tuozzo.com>, Andy Lutomirski <luto@...capital.net>, Grzegorz Andrejczuk <grzegorz.andrejczuk@...el.com>, Masahiro Yamada <yamada.masahiro@...ionext.com>, linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org, kernel-hardening@...ts.openwall.com Subject: Re: [PATCH v2] binfmt_elf: Use ELF_ET_DYN_BASE only for PIE On Wed, 2017-06-21 at 10:32 -0700, Kees Cook wrote: > To allow for a lower ELF_ET_DYN_BASE, loaders (ET_DYN without INTERP) > are loaded into the mmap region, leaving space available for either > an > ET_EXEC binary with a fixed location or PIE being loaded into mmap by > the > loader. Only PIE programs are loaded offset from ELF_ET_DYN_BASE, > which > means architectures can now safely lower their values without risk of > loaders colliding with their subsequently loaded programs. > > For 64-bit, ELF_ET_DYN_BASE is best set to 4GB to allow runtimes to > use > the entire 32-bit address space for 32-bit pointers. > > Thanks to PaX Team, Daniel Micay, and Rik van Riel for inspiration > and > suggestions on how to implement this solution. > > Fixes: d1fd836dcf00 ("mm: split ET_DYN ASLR from mmap ASLR") > Cc: stable@...r.kernel.org > Signed-off-by: Kees Cook <keescook@...omium.org> Acked-by: Rik van Riel <riel@...hat.com>
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