From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: ARC-Seal: i=1; a=rsa-sha256; t=1521827752; cv=none; d=google.com; s=arc-20160816; b=U6gFmjYKAYYBn4nMDqbvYGR43l/F/65lya4QhJewm5ZvSuPYk9ETd8et0plH7Y7XJJ s4wNBBFzMtM9nrx2K8q5rRNJ7h2IspTcwxPGupSSkzq4GZttRcOoeZKrCcVJptP5ZePG Eluzf4IZc/Vw+qQQEG3CRb8aq3oFW/7n4dKv3DJLOGtc9qSiYP7Fpvqyn9sI5XheTvAa DlR8VPLBeCWEs3CAgkjqKE219lIo83eEodE9glrxY06GjclWqdfVW2GfFsiv+ISnKjOP q8BOwkJmnx9wu95rl9JzZpY9k8v7iWPwRyvii73/FhKPepC/63paYUdqSuCCbqU0O3eq oAjw== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=to:references:message-id:content-transfer-encoding:cc:date :in-reply-to:from:subject:mime-version:dkim-signature :arc-authentication-results; bh=Nn/LegfdgCnPMfgxrP8ldElW5x41AbmrS9XnJZIcO0M=; b=LWmtTWdQvzW0UsuMc06qAAb6CHb3ELLCGt4KVK6jOtc64IXdwurw7Yflvhun1gtLu0 DkvALCQM146HBUEeuMDIRlJti/vWewwFC1WiQU8TGM8jU1MTy68/PwDPs6mEc1x/JHBR sddD9zLV4AvSy8eaEbp1sUUTSAeKPOy9FCWmhW/R8XeavfOZJLuNz9sxmt2t8Ym1xSmV n0SswJP6iaAwm9X+sXDLTibVTX5+H5XASAvXlst1xJreZwJgZpkobEOY2iYdDESj38mI EIE+R9Zeo9JMIHiU+KksUDOlwTRk3be3QUTHAZwE/Yagyk3jaFot0t747axfxynGk/Mr nZGQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=dmuwuz6Z; spf=pass (google.com: domain of blackzert@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=blackzert@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com Authentication-Results: mx.google.com; dkim=pass header.i=@gmail.com header.s=20161025 header.b=dmuwuz6Z; spf=pass (google.com: domain of blackzert@gmail.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=blackzert@gmail.com; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=gmail.com X-Google-Smtp-Source: AG47ELvfGoHwG8ZFUTfHtGgnMEMhX5286YUod0rhOtxN+bKDVeOxka7156ZLffopag3GbBdCfb+X5Q== 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 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 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> To: Matthew Wilcox X-Mailer: Apple Mail (2.3445.5.20) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: =?utf-8?q?1595656488556903336?= X-GMAIL-MSGID: =?utf-8?q?1595752056978107135?= X-Mailing-List: linux-kernel@vger.kernel.org List-ID: > 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.=