From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f197.google.com (mail-wr0-f197.google.com [209.85.128.197]) by kanga.kvack.org (Postfix) with ESMTP id 925466B0038 for ; Fri, 1 Dec 2017 10:20:11 -0500 (EST) Received: by mail-wr0-f197.google.com with SMTP id w95so6008678wrc.20 for ; Fri, 01 Dec 2017 07:20:11 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id u26si1069399eda.521.2017.12.01.07.20.10 for (version=TLS1 cipher=AES128-SHA bits=128/128); Fri, 01 Dec 2017 07:20:10 -0800 (PST) Subject: Re: [PATCH v4 3/3] mm/mempolicy: add nodes_empty check in SYSC_migrate_pages References: <1512122128-6220-1-git-send-email-xieyisheng1@huawei.com> From: Vlastimil Babka Message-ID: <305e9b37-0e58-a53d-55b7-f0815c1ba64f@suse.cz> Date: Fri, 1 Dec 2017 16:18:42 +0100 MIME-Version: 1.0 In-Reply-To: <1512122128-6220-1-git-send-email-xieyisheng1@huawei.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Yisheng Xie , akpm@linux-foundation.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, Andi Kleen , Chris Salls , Christopher Lameter , David Rientjes , Ingo Molnar , Naoya Horiguchi , Tan Xiaojun On 12/01/2017 10:55 AM, Yisheng Xie wrote: > As in manpage of migrate_pages, the errno should be set to EINVAL when > none of the node IDs specified by new_nodes are on-line and allowed by the > process's current cpuset context, or none of the specified nodes contain > memory. However, when test by following case: > > new_nodes = 0; > old_nodes = 0xf; > ret = migrate_pages(pid, old_nodes, new_nodes, MAX); > > The ret will be 0 and no errno is set. As the new_nodes is empty, we > should expect EINVAL as documented. > > To fix the case like above, this patch check whether target nodes AND > current task_nodes is empty, and then check whether AND > node_states[N_MEMORY] is empty. > > Meanwhile,this patch also remove the check of EPERM on CAP_SYS_NICE. > The caller of migrate_pages should be able to migrate the target process > pages anywhere the caller can allocate memory, if the caller can access > the mm_struct. > > Signed-off-by: Yisheng Xie > Cc: Andi Kleen > Cc: Chris Salls > Cc: Christopher Lameter > Cc: David Rientjes > Cc: Ingo Molnar > Cc: Naoya Horiguchi > Cc: Tan Xiaojun > Cc: Vlastimil Babka > --- > v3: > * check whether node is empty after AND current task node, and then nodes > which have memory > v4: > * remove the check of EPERM on CAP_SYS_NICE. > > Hi Vlastimil and Christopher, > > Could you please help to review this version? Hi, I think we should stay with v3 after all. What I missed when reviewing it, is that the EPERM check is for cpuset_mems_allowed(task) and in v3 you add EINVAL check for cpuset_mems_allowed(current), which may not be the same, and the intention of CAP_SYS_NICE is not whether we can bypass our own cpuset, but whether we can bypass the target task's cpuset. Sorry for the confusion. > Thanks > Yisheng Xie > > mm/mempolicy.c | 13 +++++-------- > 1 file changed, 5 insertions(+), 8 deletions(-) > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index 65df28d..4da74b6 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -1426,17 +1426,14 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode, > } > rcu_read_unlock(); > > - task_nodes = cpuset_mems_allowed(task); > - /* Is the user allowed to access the target nodes? */ > - if (!nodes_subset(*new, task_nodes) && !capable(CAP_SYS_NICE)) { > - err = -EPERM; > + task_nodes = cpuset_mems_allowed(current); > + nodes_and(*new, *new, task_nodes); > + if (nodes_empty(*new)) > goto out_put; > - } > > - if (!nodes_subset(*new, node_states[N_MEMORY])) { > - err = -EINVAL; > + nodes_and(*new, *new, node_states[N_MEMORY]); > + if (nodes_empty(*new)) > goto out_put; > - } > > err = security_task_movememory(task); > if (err) > -- 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