From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-it0-f72.google.com (mail-it0-f72.google.com [209.85.214.72]) by kanga.kvack.org (Postfix) with ESMTP id 4E6B06B002C for ; Wed, 28 Mar 2018 00:50:11 -0400 (EDT) Received: by mail-it0-f72.google.com with SMTP id m134-v6so1484086itb.9 for ; Tue, 27 Mar 2018 21:50:11 -0700 (PDT) Received: from mail-sor-f65.google.com (mail-sor-f65.google.com. [209.85.220.65]) by mx.google.com with SMTPS id n3-v6sor1486917ite.114.2018.03.27.21.50.10 for (Google Transport Security); Tue, 27 Mar 2018 21:50:10 -0700 (PDT) Subject: Re: [RFC PATCH v2 0/2] Randomization of address chosen by mmap. References: <1521736598-12812-1-git-send-email-blackzert@gmail.com> <20180323124806.GA5624@bombadil.infradead.org> <20180323180024.GB1436@brightrain.aerifal.cx> <20180323190618.GA23763@bombadil.infradead.org> From: Rob Landley Message-ID: <7e41ef7a-0bac-02fe-21fd-a1ed86c22230@landley.net> Date: Tue, 27 Mar 2018 23:50:02 -0500 MIME-Version: 1.0 In-Reply-To: <20180323190618.GA23763@bombadil.infradead.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox , Rich Felker Cc: Ilya Smith , rth@twiddle.net, ink@jurassic.park.msu.ru, mattst88@gmail.com, vgupta@synopsys.com, linux@armlinux.org.uk, tony.luck@intel.com, fenghua.yu@intel.com, jhogan@kernel.org, ralf@linux-mips.org, jejb@parisc-linux.org, deller@gmx.de, benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, ysato@users.sourceforge.jp, davem@davemloft.net, tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, x86@kernel.org, nyc@holomorphy.com, viro@zeniv.linux.org.uk, arnd@arndb.de, gregkh@linuxfoundation.org, deepa.kernel@gmail.com, mhocko@suse.com, hughd@google.com, kstewart@linuxfoundation.org, pombredanne@nexb.com, akpm@linux-foundation.org, steve.capper@arm.com, punit.agrawal@arm.com, paul.burton@mips.com, aneesh.kumar@linux.vnet.ibm.com, npiggin@gmail.com, keescook@chromium.org, bhsharma@redhat.com, riel@redhat.com, nitin.m.gupta@oracle.com, kirill.shutemov@linux.intel.com, dan.j.williams@intel.com, jack@suse.cz, ross.zwisler@linux.intel.com, jglisse@redhat.com, aarcange@redhat.com, oleg@redhat.com, linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-ia64@vger.kernel.org, linux-metag@vger.kernel.org, linux-mips@linux-mips.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, linux-mm@kvack.org On 03/23/2018 02:06 PM, Matthew Wilcox wrote: > On Fri, Mar 23, 2018 at 02:00:24PM -0400, Rich Felker wrote: >> On Fri, Mar 23, 2018 at 05:48:06AM -0700, Matthew Wilcox wrote: >>> On Thu, Mar 22, 2018 at 07:36:36PM +0300, Ilya Smith wrote: >>>> Current implementation doesn't randomize address returned by mmap. >>>> All the entropy ends with choosing mmap_base_addr at the process >>>> creation. After that mmap build very predictable layout of address >>>> space. It allows to bypass ASLR in many cases. This patch make >>>> randomization of address on any mmap call. >>> >>> Why should this be done in the kernel rather than libc? libc is perfectly >>> capable of specifying random numbers in the first argument of mmap. >> >> Generally libc does not have a view of the current vm maps, and thus >> in passing "random numbers", they would have to be uniform across the >> whole vm space and thus non-uniform once the kernel rounds up to avoid >> existing mappings. > > I'm aware that you're the musl author, but glibc somehow manages to > provide etext, edata and end, demonstrating that it does know where at > least some of the memory map lies. You can parse /proc/self/maps, but it's really expensive and disgusting. Rob