From 9f267393b036f1470fb12fb892d59e7ff8aeb58d Mon Sep 17 00:00:00 2001 From: Tetsuo Handa Date: Thu, 25 Aug 2022 17:38:38 +0900 Subject: [PATCH] cgroup: Add missing cpus_read_lock() to cgroup_attach_task_all() commit 43626dade36fa74d3329046f4ae2d7fdefe401c6 upstream. syzbot is hitting percpu_rwsem_assert_held(&cpu_hotplug_lock) warning at cpuset_attach() [1], for commit 4f7e7236435ca0ab ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock") missed that cpuset_attach() is also called from cgroup_attach_task_all(). Add cpus_read_lock() like what cgroup_procs_write_start() does. Link: https://syzkaller.appspot.com/bug?extid=29d3a3b4d86c8136ad9e [1] Reported-by: syzbot Signed-off-by: Tetsuo Handa Fixes: 4f7e7236435ca0ab ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock") Signed-off-by: Tejun Heo Signed-off-by: Greg Kroah-Hartman --- kernel/cgroup/cgroup-v1.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/cgroup/cgroup-v1.c b/kernel/cgroup/cgroup-v1.c index 1a0a9f820c69..433b9e840b38 100644 --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -57,6 +57,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) int retval = 0; mutex_lock(&cgroup_mutex); + cpus_read_lock(); percpu_down_write(&cgroup_threadgroup_rwsem); for_each_root(root) { struct cgroup *from_cgrp; @@ -73,6 +74,7 @@ int cgroup_attach_task_all(struct task_struct *from, struct task_struct *tsk) break; } percpu_up_write(&cgroup_threadgroup_rwsem); + cpus_read_unlock(); mutex_unlock(&cgroup_mutex); return retval;