From mboxrd@z Thu Jan 1 00:00:00 1970 From: Waiman Long Subject: [PATCH] cpuset: Enforce that a child's cpus must be a subset of the parent Date: Wed, 30 May 2018 09:46:31 -0400 Message-ID: <1527687991-1431-1-git-send-email-longman@redhat.com> Return-path: Sender: linux-kernel-owner@vger.kernel.org List-ID: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: Tejun Heo , Li Zefan , Johannes Weiner , Peter Zijlstra , Ingo Molnar Cc: cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, kernel-team@fb.com, pjt@google.com, luto@amacapital.net, Mike Galbraith , torvalds@linux-foundation.org, Roman Gushchin , Juri Lelli , Patrick Bellasi , Waiman Long It was found that the cpuset.cpus could contain CPUs that are not listed in their parent's cpu list as shown by the command sequence below: # echo "+cpuset" >cgroup.subtree_control # mkdir g1 # echo 0-5 >g1/cpuset.cpus # mkdir g1/g11 # echo "+cpuset" > g1/cgroup.subtree_control # echo 6-11 >g1/g11/cpuset.cpus # grep -R . g1 | grep "\.cpus" g1/cpuset.cpus:0-5 g1/cpuset.cpus.effective:0-5 g1/g11/cpuset.cpus:6-11 g1/g11/cpuset.cpus.effective:0-5 As the intersection of g11's cpus and that of g1 is empty, the effective cpus of g11 is just that of g1. The check in update_cpumask() is now corrected to make sure that cpus in a child cpus must be a subset of its parent's cpus. The error "write error: Invalid argument" will now be reported in the above case. Reported-by: Juri Lelli Signed-off-by: Waiman Long --- kernel/cgroup/cpuset.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 71fb2d0..ceec438 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1185,12 +1185,17 @@ static int update_cpumask(struct cpuset *cs, struct cpuset *trialcs, if (!*buf) { cpumask_clear(trialcs->cpus_allowed); } else { + struct cpuset *parent = parent_cs(cs); + retval = cpulist_parse(buf, trialcs->cpus_allowed); if (retval < 0) return retval; + /* + * The cpu list must be a subset of the parent. + */ if (!cpumask_subset(trialcs->cpus_allowed, - top_cpuset.cpus_allowed)) + parent->cpus_allowed)) return -EINVAL; } -- 1.8.3.1