From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ig0-f174.google.com (mail-ig0-f174.google.com [209.85.213.174]) by kanga.kvack.org (Postfix) with ESMTP id 6DE656B0253 for ; Tue, 3 Nov 2015 19:04:13 -0500 (EST) Received: by igvi2 with SMTP id i2so79673637igv.0 for ; Tue, 03 Nov 2015 16:04:13 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id ax3si43266igc.53.2015.11.03.16.04.12 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 03 Nov 2015 16:04:12 -0800 (PST) Date: Tue, 3 Nov 2015 16:04:10 -0800 From: Andrew Morton Subject: Re: [PATCH v2 1/2] mm: mmap: Add new /proc tunable for mmap_base ASLR. Message-Id: <20151103160410.34bbebc805c17d2f41150a19@linux-foundation.org> In-Reply-To: <1446574204-15567-1-git-send-email-dcashman@android.com> References: <1446574204-15567-1-git-send-email-dcashman@android.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Daniel Cashman Cc: linux-kernel@vger.kernel.org, linux@arm.linux.org.uk, keescook@chromium.org, mingo@kernel.org, linux-arm-kernel@lists.infradead.org, corbet@lwn.net, dzickus@redhat.com, ebiederm@xmission.com, xypron.glpk@gmx.de, jpoimboe@redhat.com, kirill.shutemov@linux.intel.com, n-horiguchi@ah.jp.nec.com, aarcange@redhat.com, mgorman@suse.de, tglx@linutronix.de, rientjes@google.com, linux-mm@kvack.org, linux-doc@vger.kernel.org, salyzyn@android.com, jeffv@google.com, nnk@google.com, dcashman On Tue, 3 Nov 2015 10:10:03 -0800 Daniel Cashman wrote: > ASLR currently only uses 8 bits to generate the random offset for the > mmap base address on 32 bit architectures. This value was chosen to > prevent a poorly chosen value from dividing the address space in such > a way as to prevent large allocations. This may not be an issue on all > platforms. Allow the specification of a minimum number of bits so that > platforms desiring greater ASLR protection may determine where to place > the trade-off. Can we please include a very good description of the motivation for this change? What is inadequate about the current code, what value does the enhancement have to our users, what real-world problems are being solved, etc. Because all we have at present is "greater ASLR protection", which doesn't really tell anyone anything. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org