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cpuset: Fix unsafe lock order between cpuset lock and cpuslock

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The backport commit 4eec5fe1c680a ("cgroup/cpuset: Fix a race
between cpuset_attach() and cpu hotplug") looks suspicious since
it comes before commit d74b27d63a8b ("cgroup/cpuset: Change
cpuset_rwsem and hotplug lock order") v5.4-rc1~176^2~30 when
the locking order was: cpuset lock, cpus lock.

Fix it with the correct locking order and reduce the cpus locking
range because only set_cpus_allowed_ptr() needs the protection of
cpus lock.

Fixes: 4eec5fe1c680a ("cgroup/cpuset: Fix a race between cpuset_attach() and cpu hotplug")
Reported-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Zhang Qiao <zhangqiao22@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Zhang Qiao 2022-03-17 10:41:57 +08:00 committed by Greg Kroah-Hartman
parent 1ba1ec1946
commit aa44002e7d
1 changed files with 6 additions and 2 deletions
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8
kernel/cgroup/cpuset.c
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@ -1528,9 +1528,13 @@ static void cpuset_attach(struct cgroup_taskset *tset)
cgroup_taskset_first(tset, &css);
cs = css_cs(css);
cpus_read_lock();
mutex_lock(&cpuset_mutex);
/*
* It should hold cpus lock because a cpu offline event can
* cause set_cpus_allowed_ptr() failed.
*/
get_online_cpus();
/* prepare for attach */
if (cs == &top_cpuset)
cpumask_copy(cpus_attach, cpu_possible_mask);
@ -1549,6 +1553,7 @@ static void cpuset_attach(struct cgroup_taskset *tset)
cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
cpuset_update_task_spread_flag(cs, task);
}
put_online_cpus();
/*
* Change mm for all threadgroup leaders. This is expensive and may
@ -1584,7 +1589,6 @@ static void cpuset_attach(struct cgroup_taskset *tset)
wake_up(&cpuset_attach_wq);
mutex_unlock(&cpuset_mutex);
cpus_read_unlock();
}
/* The various types of files and directories in a cpuset file system */