From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf0-f70.google.com (mail-lf0-f70.google.com [209.85.215.70]) by kanga.kvack.org (Postfix) with ESMTP id CDF376B002F for ; Fri, 23 Mar 2018 13:55:53 -0400 (EDT) Received: by mail-lf0-f70.google.com with SMTP id m16-v6so4198520lfc.0 for ; Fri, 23 Mar 2018 10:55:53 -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 d8sor1709388ljj.89.2018.03.23.10.55.52 for (Google Transport Security); Fri, 23 Mar 2018 10:55:52 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 11.2 \(3445.5.20\)) Subject: Re: [RFC PATCH v2 0/2] Randomization of address chosen by mmap. From: Ilya Smith In-Reply-To: <20180323124806.GA5624@bombadil.infradead.org> Date: Fri, 23 Mar 2018 20:55:49 +0300 Content-Transfer-Encoding: quoted-printable Message-Id: <651E0DB6-4507-4DA1-AD46-9C26ED9792A8@gmail.com> References: <1521736598-12812-1-git-send-email-blackzert@gmail.com> <20180323124806.GA5624@bombadil.infradead.org> Sender: owner-linux-mm@kvack.org List-ID: To: Matthew Wilcox Cc: 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, ralf@linux-mips.org, jejb@parisc-linux.org, Helge Deller , benh@kernel.crashing.org, paulus@samba.org, mpe@ellerman.id.au, schwidefsky@de.ibm.com, heiko.carstens@de.ibm.com, ysato@users.sourceforge.jp, dalias@libc.org, 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, Michal Hocko , Hugh Dickins , kstewart@linuxfoundation.org, pombredanne@nexb.com, Andrew Morton , steve.capper@arm.com, punit.agrawal@arm.com, aneesh.kumar@linux.vnet.ibm.com, npiggin@gmail.com, Kees Cook , bhsharma@redhat.com, riel@redhat.com, nitin.m.gupta@oracle.com, "Kirill A. Shutemov" , Dan Williams , Jan Kara , ross.zwisler@linux.intel.com, Jerome Glisse , Andrea Arcangeli , Oleg Nesterov , linux-alpha@vger.kernel.org, LKML , linux-snps-arc@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 > On 23 Mar 2018, at 15:48, Matthew Wilcox wrote: >=20 > 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. >=20 > 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. Well, there is following reasons: 1. It should be done in any libc implementation, what is not possible = IMO; 2. User mode is not that layer which should be responsible for choosing random address or handling entropy; 3. Memory fragmentation is unpredictable in this case Off course user mode could use random =E2=80=98hint=E2=80=99 address, = but kernel may discard this address if it is occupied for example and allocate just = before closest vma. So this solution doesn=E2=80=99t give that much security = like=20 randomization address inside kernel.=