From mboxrd@z Thu Jan 1 00:00:00 1970 From: Yisheng Xie Subject: Re: [PATCH RFC v2 1/4] mm/mempolicy: Fix get_nodes() mask miscalculation Date: Wed, 1 Nov 2017 17:37:36 +0800 Message-ID: References: <1509099265-30868-1-git-send-email-xieyisheng1@huawei.com> <1509099265-30868-2-git-send-email-xieyisheng1@huawei.com> <922a4767-9eed-40aa-c437-6f6fcdcab150@suse.cz> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <922a4767-9eed-40aa-c437-6f6fcdcab150-AlSwsSmVLrQ@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Vlastimil Babka , akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org, mhocko-IBi9RG/b67k@public.gmane.org, mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, rientjes-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org, n-horiguchi-PaJj6Psr51x8UrSeD/g0lQ@public.gmane.org, salls-b3bnyZ7c9ISVc3sceRu5cw@public.gmane.org Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, tanxiaojun-hv44wF8Li93QT0dZR+AlfA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andi Kleen List-Id: linux-api@vger.kernel.org Hi Vlastimil, Thanks for comment! On 2017/10/31 16:34, Vlastimil Babka wrote: > On 10/27/2017 12:14 PM, Yisheng Xie wrote: >> It appears there is a nodemask miscalculation in the get_nodes() >> function in mm/mempolicy.c. This bug has two effects: >> >> 1. It is impossible to specify a length 1 nodemask. >> 2. It is impossible to specify a nodemask containing the last node. > > This should be more specific, which syscalls are you talking about? > I assume it's set_mempolicy() and mbind() and it's the same issue that > was discussed at https://marc.info/?l=linux-mm&m=150732591909576&w=2 ? I just missed this thread, sorry about that. Not only set_mempolicy() and mbind(), but migrate_pages() also suffers this problem. Maybe related manpage should documented this as your mentioned below. Thanks Yisheng Xie > >> Brent have submmit a patch before v2.6.12, however, Andi revert his >> changed for ABI problem. I just resent this patch as RFC, for do not >> clear about what's the problem Andi have met. > > You should have CC'd Andi. As was discussed in the other thread, this > would make existing programs potentially unsafe, so we can't change it. > Instead it should be documented. > >> As manpage of set_mempolicy, If the value of maxnode is zero, the >> nodemask argument is ignored. but we should not ignore the nodemask >> when maxnode is 1. >>