linux-kernel - [PATCH cgroup/for-4.13-fixes] cgroup: create dfl

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: <20170718215746.GG3365493@devbig577.frc2.facebook.com>
Date:   Tue, 18 Jul 2017 17:57:46 -0400
From:   Tejun Heo <tj@...nel.org>
To:     Waiman Long <longman@...hat.com>
Cc:     Li Zefan <lizefan@...wei.com>,
        Johannes Weiner <hannes@...xchg.org>, cgroups@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH cgroup/for-4.13-fixes] cgroup: create dfl_root files on
 subsys registration

On subsystem registration, css_populate_dir() is not called on the new
root css, so the interface files for the subsystem on cgrp_dfl_root
aren't created on registration.  This is a residue from the days when
cgrp_dfl_root was used only as the parking spot for unused subsystems,
which no longer is true as it's used as the root for cgroup2.

This is often fine as later operations tend to create them as a part
of mount (cgroup1) or subtree_control operations (cgroup2); however,
it's not difficult to mount cgroup2 with the controller interface
files missing as Waiman found out.

Fix it by invoking css_populate_dir() on the root css on subsys
registration.

Signed-off-by: Tejun Heo <tj@...nel.org>
Reported-by: Waiman Long <longman@...hat.com>
Cc: stable@...r.kernel.org # v4.5+
---
Hello, Waiman.

Can you please verify that this fixes the bug?

Thanks.

 kernel/cgroup/cgroup.c |    4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 620794a..9d33108 100644
--- a/kernel/cgroup/cgroup.c
+++ b/kernel/cgroup/cgroup.c
@@ -4669,6 +4669,10 @@ int __init cgroup_init(void)

 		if (ss->bind)
 			ss->bind(init_css_set.subsys[ssid]);
+
+		mutex_lock(&cgroup_mutex);
+		css_populate_dir(init_css_set.subsys[ssid]);
+		mutex_unlock(&cgroup_mutex);
 	}

 	/* init_css_set.subsys[] has been updated, re-hash */