From 9fcc65d0f0b0e35e34e432f9a43756040523035c Mon Sep 17 00:00:00 2001 From: Zhang Qiao Date: Sat, 7 May 2022 08:24:35 +0000 Subject: [PATCH] cpuset: Fix unsafe lock order between cpuset lock and cpuslock MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit stable inclusion from linux-4.19.236 commit aa44002e7db25f333ddf412fb81e8db6c100841a category: bugfix bugzilla: https://gitee.com/openeuler/kernel/issues/I5646A CVE: NA -------------------------------- 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 Signed-off-by: Zhang Qiao Signed-off-by: Greg Kroah-Hartman Signed-off-by: Yongqiang Liu --- kernel/cgroup/cpuset.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/kernel/cgroup/cpuset.c b/kernel/cgroup/cpuset.c index 27dd33566df8..3544ee391350 100644 --- a/kernel/cgroup/cpuset.c +++ b/kernel/cgroup/cpuset.c @@ -1530,9 +1530,13 @@ 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); @@ -1551,6 +1555,7 @@ 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 @@ -1586,7 +1591,6 @@ 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 */ -- GitLab