From: Zhang Qiao <zhangqiao22@huawei.com>
Date: Fri, 21 Jan 2022 18:12:10 +0800
Subject: cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug
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Git-commit: 05c7b7a92cc87ff8d7fde189d0fade250697573c
Patch-mainline: v5.17-rc6
References: bsc#1196869
As previously discussed(https://lkml.org/lkml/2022/1/20/51),
cpuset_attach() is affected with similar cpu hotplug race,
as follow scenario:
cpuset_attach() cpu hotplug
--------------------------- ----------------------
down_write(cpuset_rwsem)
guarantee_online_cpus() // (load cpus_attach)
sched_cpu_deactivate
set_cpu_active()
// will change cpu_active_mask
set_cpus_allowed_ptr(cpus_attach)
__set_cpus_allowed_ptr_locked()
// (if the intersection of cpus_attach and
cpu_active_mask is empty, will return -EINVAL)
up_write(cpuset_rwsem)
To avoid races such as described above, protect cpuset_attach() call
with cpu_hotplug_lock.
Fixes: be367d099270 ("cgroups: let ss->can_attach and ss->attach do whole threadgroups at a time")
Cc: stable@vger.kernel.org # v2.6.32+
Reported-by: Zhao Gongyi <zhaogongyi@huawei.com>
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Reviewed-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
[mkoutny: adjust context for missing 431c69fac05b]
Acked-by: Michal Koutný <mkoutny@suse.com>
---
kernel/cgroup/cpuset.c | 2 ++
1 file changed, 2 insertions(+)
--- a/kernel/cgroup/cpuset.c
+++ b/kernel/cgroup/cpuset.c
@@ -2254,6 +2254,7 @@ static void cpuset_attach(struct cgroup_
cgroup_taskset_first(tset, &css);
cs = css_cs(css);
+ cpus_read_lock();
percpu_down_write(&cpuset_rwsem);
/* prepare for attach */
@@ -2309,6 +2310,7 @@ static void cpuset_attach(struct cgroup_
wake_up(&cpuset_attach_wq);
percpu_up_write(&cpuset_rwsem);
+ cpus_read_unlock();
}
/* The various types of files and directories in a cpuset file system */