Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755430AbbLAAsJ (ORCPT ); Mon, 30 Nov 2015 19:48:09 -0500 Received: from mail-pa0-f53.google.com ([209.85.220.53]:33342 "EHLO mail-pa0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754788AbbLAAsG (ORCPT ); Mon, 30 Nov 2015 19:48:06 -0500 Subject: Re: [PATCH v4 1/4] mm: mmap: Add new /proc tunable for mmap_base ASLR. To: Andrew Morton , Kees Cook References: <1448578785-17656-1-git-send-email-dcashman@android.com> <1448578785-17656-2-git-send-email-dcashman@android.com> <20151130155412.b1a087f4f6f4d4180ab4472d@linux-foundation.org> <20151130160118.e43a2e53a59e347a95a94d5c@linux-foundation.org> <20151130161811.592c205d8dc7b00f44066a37@linux-foundation.org> Cc: LKML , Russell King - ARM Linux , Ingo Molnar , "linux-arm-kernel@lists.infradead.org" , Jonathan Corbet , Don Zickus , "Eric W. Biederman" , Heinrich Schuchardt , jpoimboe@redhat.com, "Kirill A. Shutemov" , n-horiguchi@ah.jp.nec.com, Andrea Arcangeli , Mel Gorman , Thomas Gleixner , David Rientjes , Linux-MM , "linux-doc@vger.kernel.org" , Mark Salyzyn , Jeffrey Vander Stoep , Nick Kralevich , Catalin Marinas , Will Deacon , "H. Peter Anvin" , "x86@kernel.org" , Hector Marco , Borislav Petkov , Daniel Cashman From: Daniel Cashman Message-ID: <565CEE3D.4070008@android.com> Date: Mon, 30 Nov 2015 16:47:57 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 MIME-Version: 1.0 In-Reply-To: <20151130161811.592c205d8dc7b00f44066a37@linux-foundation.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2588 Lines: 72 On 11/30/15 4:18 PM, Andrew Morton wrote: > On Mon, 30 Nov 2015 16:04:36 -0800 Kees Cook wrote: > >>>>> +#ifdef CONFIG_HAVE_ARCH_MMAP_RND_BITS >>>>> + { >>>>> + .procname = "mmap_rnd_bits", >>>>> + .data = &mmap_rnd_bits, >>>>> + .maxlen = sizeof(mmap_rnd_bits), >>>>> + .mode = 0600, >>>>> + .proc_handler = proc_dointvec_minmax, >>>>> + .extra1 = (void *) &mmap_rnd_bits_min, >>>>> + .extra2 = (void *) &mmap_rnd_bits_max, >>>> >>>> hm, why the typecasts? They're unneeded and are omitted everywhere(?) >>>> else in kernel/sysctl.c. >>> >>> Oh. Casting away constness. >>> >>> What's the thinking here? They can change at any time so they aren't >>> const so we shouldn't declare them to be const? >> >> The _min and _max values shouldn't be changing: they're decided based >> on the various CONFIG options that calculate the valid min/maxes. Only >> mmap_rnd_bits itself should be changing. > > hmpf. > > From: Andrew Morton > Subject: include/linux/sysctl.h: make ctl_table.extra1/2 const > > Nothing should be altering these values. Declare the pointed-to values to > be const so we can actually use const values. > > Cc: Kees Cook > Cc: Daniel Cashman > Signed-off-by: Andrew Morton > --- > > include/linux/sysctl.h | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff -puN include/linux/sysctl.h~a include/linux/sysctl.h > --- a/include/linux/sysctl.h~a > +++ a/include/linux/sysctl.h > @@ -111,8 +111,8 @@ struct ctl_table > struct ctl_table *child; /* Deprecated */ > proc_handler *proc_handler; /* Callback for text formatting */ > struct ctl_table_poll *poll; > - void *extra1; > - void *extra2; > + const void *extra1; > + const void *extra2; > }; > > struct ctl_node { > diff -puN kernel/sysctl.c~a kernel/sysctl.c > _ This looks good to me, thanks! I hadn't gone through all of the uses of extra1 and extra2, nor did I think the change herein was conceptually a part of mine, so I casted-away in order to indicate intent, while leaving the change here as a possibility if ctl_table could be altered for all use-cases. Thank You, Dan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/