This is a note to let you know that I've just added the patch titled cgroup: Add missing cpus_read_lock() to cgroup_attach_task_all() to the 4.19-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: cgroup-add-missing-cpus_read_lock-to-cgroup_attach_task_all.patch and it can be found in the queue-4.19 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From caixinchen1@xxxxxxxxxx Mon Mar 20 02:20:45 2023 From: Cai Xinchen <caixinchen1@xxxxxxxxxx> Date: Mon, 20 Mar 2023 01:15:07 +0000 Subject: cgroup: Add missing cpus_read_lock() to cgroup_attach_task_all() To: <longman@xxxxxxxxxx>, <lizefan.x@xxxxxxxxxxxxx>, <tj@xxxxxxxxxx>, <hannes@xxxxxxxxxxx>, <gregkh@xxxxxxxxxxxxxxxxxxx>, <sashal@xxxxxxxxxx> Cc: <mkoutny@xxxxxxxx>, <zhangqiao22@xxxxxxxxxx>, <juri.lelli@xxxxxxxxxx>, <penguin-kernel@xxxxxxxxxxxxxxxxxxx>, <stable@xxxxxxxxxxxxxxx>, <cgroups@xxxxxxxxxxxxxxx>, <linux-kernel@xxxxxxxxxxxxxxx> Message-ID: <20230320011507.129441-4-caixinchen1@xxxxxxxxxx> From: Cai Xinchen <caixinchen1@xxxxxxxxxx> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> 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 <syzbot+29d3a3b4d86c8136ad9e@xxxxxxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Fixes: 4f7e7236435ca0ab ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock") Signed-off-by: Tejun Heo <tj@xxxxxxxxxx> Signed-off-by: Cai Xinchen <caixinchen1@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- kernel/cgroup/cgroup-v1.c | 3 +++ 1 file changed, 3 insertions(+) --- a/kernel/cgroup/cgroup-v1.c +++ b/kernel/cgroup/cgroup-v1.c @@ -13,6 +13,7 @@ #include <linux/delayacct.h> #include <linux/pid_namespace.h> #include <linux/cgroupstats.h> +#include <linux/cpu.h> #include <trace/events/cgroup.h> @@ -55,6 +56,7 @@ int cgroup_attach_task_all(struct task_s int retval = 0; mutex_lock(&cgroup_mutex); + get_online_cpus(); percpu_down_write(&cgroup_threadgroup_rwsem); for_each_root(root) { struct cgroup *from_cgrp; @@ -71,6 +73,7 @@ int cgroup_attach_task_all(struct task_s break; } percpu_up_write(&cgroup_threadgroup_rwsem); + put_online_cpus(); mutex_unlock(&cgroup_mutex); return retval; Patches currently in stable-queue which might be from caixinchen1@xxxxxxxxxx are queue-4.19/cgroup-cpuset-change-cpuset_rwsem-and-hotplug-lock-order.patch queue-4.19/cgroup-fix-threadgroup_rwsem-cpus_read_lock-deadlock.patch queue-4.19/cgroup-add-missing-cpus_read_lock-to-cgroup_attach_task_all.patch