From b857ec7d436f6fbb8c33e8d6a16d2f16175517d8 Mon Sep 17 00:00:00 2001
From: Topi Miettinen <toiwoton@gmail.com>
Date: Sun, 10 Jul 2016 11:45:30 +0300
Subject: [PATCH] cgroup: check options and capabilities before locking to
avoid a deadlock
Signed-off-by: Topi Miettinen <toiwoton@gmail.com>
---
kernel/cgroup.c | 30 +++++++++++++++---------------
1 file changed, 15 insertions(+), 15 deletions(-)
@@ -2100,6 +2100,21 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
return ERR_PTR(-EPERM);
}
+ /* First find the desired set of subsystems */
+ ret = parse_cgroupfs_options(data, &opts);
+ if (ret)
+ goto out_free;
+
+ /*
+ * We know this subsystem has not yet been bound. Users in a non-init
+ * user namespace may only mount hierarchies with no bound subsystems,
+ * i.e. 'none,name=user1'
+ */
+ if (!opts.none && !capable(CAP_SYS_ADMIN)) {
+ ret = -EPERM;
+ goto out_free;
+ }
+
/*
* The first time anyone tries to mount a cgroup, enable the list
* linking each css_set to its tasks and fix up all existing tasks.
@@ -2121,11 +2136,6 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);
- /* First find the desired set of subsystems */
- ret = parse_cgroupfs_options(data, &opts);
- if (ret)
- goto out_unlock;
-
/*
* Destruction of cgroup root is asynchronous, so subsystems may
* still be dying after the previous unmount. Let's drain the
@@ -2216,16 +2226,6 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type,
goto out_unlock;
}
- /*
- * We know this subsystem has not yet been bound. Users in a non-init
- * user namespace may only mount hierarchies with no bound subsystems,
- * i.e. 'none,name=user1'
- */
- if (!opts.none && !capable(CAP_SYS_ADMIN)) {
- ret = -EPERM;
- goto out_unlock;
- }
-
root = kzalloc(sizeof(*root), GFP_KERNEL);
if (!root) {
ret = -ENOMEM;
--
2.8.1