linux-kernel - [PATCH 13/14] device_cgroup: use css_has_online_children() instead of has

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Date:	Fri,  9 May 2014 17:31:30 -0400
From:	Tejun Heo <tj@...nel.org>
To:	lizefan@...wei.com
Cc:	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	hannes@...xchg.org, Tejun Heo <tj@...nel.org>,
	Aristeu Rozanski <aris@...hat.com>,
	Serge Hallyn <serge.hallyn@...ntu.com>
Subject: [PATCH 13/14] device_cgroup: use css_has_online_children() instead of has_children()

devcgroup_update_access() wants to know whether there are child
cgroups which are online and visible to userland and has_children()
may return false positive.  Replace it with css_has_online_children().

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Aristeu Rozanski <aris@...hat.com>
Cc: Serge Hallyn <serge.hallyn@...ntu.com>
---
 security/device_cgroup.c | 19 ++-----------------
 1 file changed, 2 insertions(+), 17 deletions(-)

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 75b4b18..22de334 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -475,21 +475,6 @@ static int propagate_exception(struct dev_cgroup *devcg_root,
 	return rc;
 }
 
-static inline bool has_children(struct dev_cgroup *devcgroup)
-{
-	bool ret;
-
-	/*
-	 * FIXME: There may be lingering offline csses and this function
-	 * may return %true when there isn't any userland-visible child
-	 * which is incorrect for our purposes.
-	 */
-	rcu_read_lock();
-	ret = css_next_child(NULL, &devcgroup->css);
-	rcu_read_unlock();
-	return ret;
-}
-
 /*
  * Modify the exception list using allow/deny rules.
  * CAP_SYS_ADMIN is needed for this.  It's at least separate from CAP_MKNOD
@@ -522,7 +507,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
 	case 'a':
 		switch (filetype) {
 		case DEVCG_ALLOW:
-			if (has_children(devcgroup))
+			if (css_has_online_children(&devcgroup->css))
 				return -EINVAL;
 
 			if (!may_allow_all(parent))
@@ -538,7 +523,7 @@ static int devcgroup_update_access(struct dev_cgroup *devcgroup,
 				return rc;
 			break;
 		case DEVCG_DENY:
-			if (has_children(devcgroup))
+			if (css_has_online_children(&devcgroup->css))
 				return -EINVAL;
 
 			dev_exception_clean(devcgroup);
-- 
1.9.0

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