linux-kernel - [PATCH] cgroup: Add missing cpus_read_lock() to cgroup_attach_task

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <cb0b22e1-0d55-cb06-7401-37581c18169b@I-love.SAKURA.ne.jp>
Date:   Thu, 25 Aug 2022 17:38:38 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:     Tejun Heo <tj@...nel.org>, Imran Khan <imran.f.khan@...cle.com>,
        Xuewen Yan <xuewen.yan@...soc.com>
Cc:     syzbot <syzbot+29d3a3b4d86c8136ad9e@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com
Subject: [PATCH] cgroup: Add missing cpus_read_lock() to
 cgroup_attach_task_all()

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@...kaller.appspotmail.com>
Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Fixes: 4f7e7236435ca0ab ("cgroup: Fix threadgroup_rwsem <-> cpus_read_lock() deadlock")
---
Waiting for test result from syzbot. Should we remove "static" from
cgroup_attach_lock() and call from cgroup_attach_task_all() ?

 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 2ade21b54dc4..ff6a8099eb2a 100644
--- a/kernel/cgroup/cgroup-v1.c
+++ b/kernel/cgroup/cgroup-v1.c
@@ -59,6 +59,7 @@ 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;
@@ -72,6 +73,7 @@ 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;
-- 
2.18.4