From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with ESMTP id 1FFEF6B02AD for ; Mon, 26 Jul 2010 05:49:37 -0400 (EDT) Date: Mon, 26 Jul 2010 11:49:31 +0200 From: Andi Kleen Subject: Re: [PATCH] Fix off-by-one bug in mbind() syscall implementation Message-ID: <20100726094931.GA17756@basil.fritz.box> References: <1280136498-28219-1-git-send-email-andre.przywara@amd.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1280136498-28219-1-git-send-email-andre.przywara@amd.com> Sender: owner-linux-mm@kvack.org To: Andre Przywara Cc: Andrew Morton , Andi Kleen , Christoph Lameter , linux-kernel@vger.kernel.org, linux-mm@kvack.org List-ID: On Mon, Jul 26, 2010 at 11:28:18AM +0200, Andre Przywara wrote: > When the mbind() syscall implementation processes the node mask > provided by the user, the last node is accidentally masked out. > This is present since the dawn of time (aka Before Git), I guess > nobody realized that because libnuma as the most prominent user of > mbind() uses large masks (sizeof(long)) and nobody cared if the > 64th node is not handled properly. But if the user application > defers the masking to the kernel and provides the number of valid bits > in maxnodes, there is always the last node missing. > However this also affect the special case with maxnodes=0, the manpage > reads that mbind(ptr, len, MPOL_DEFAULT, &some_long, 0, 0); should > reset the policy to the default one, but in fact it returns EINVAL. > This patch just removes the decrease-by-one statement, I hope that > there is no workaround code in the wild that relies on the bogus > behavior. Actually libnuma and likely most existing users rely on it. The only way to change it would be to add new system calls. -Andi -- 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