[PATCH 1/2] device_cgroup: add lockdep asserts

Tejun Heo tj at kernel.org
Tue Nov 6 17:16:12 UTC 2012


device_cgroup uses RCU safe ->exceptions list which is write-protected
by devcgroup_mutex and has had some issues using locking correctly.
Add lockdep asserts to utility functions so that future errors can be
easily detected.

Signed-off-by: Tejun Heo <tj at kernel.org>
Cc: stable at vger.kernel.org
Cc: Aristeu Rozanski <aris at redhat.com>
Cc: Li Zefan <lizefan at huawei.com>
Cc: Serge E. Hallyn <serge.hallyn at ubuntu.com>
---
If this looks good, I'll route it with Aristeu's earlier patch through
cgroup/for-3.7-fixes.  Thanks.

 security/device_cgroup.c |   12 ++++++++++++
 1 file changed, 12 insertions(+)

--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -82,6 +82,8 @@ static int dev_exceptions_copy(struct li
 {
 	struct dev_exception_item *ex, *tmp, *new;
 
+	lockdep_assert_held(&devcgroup_mutex);
+
 	list_for_each_entry(ex, orig, list) {
 		new = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
 		if (!new)
@@ -107,6 +109,8 @@ static int dev_exception_add(struct dev_
 {
 	struct dev_exception_item *excopy, *walk;
 
+	lockdep_assert_held(&devcgroup_mutex);
+
 	excopy = kmemdup(ex, sizeof(*ex), GFP_KERNEL);
 	if (!excopy)
 		return -ENOMEM;
@@ -137,6 +141,8 @@ static void dev_exception_rm(struct dev_
 {
 	struct dev_exception_item *walk, *tmp;
 
+	lockdep_assert_held(&devcgroup_mutex);
+
 	list_for_each_entry_safe(walk, tmp, &dev_cgroup->exceptions, list) {
 		if (walk->type != ex->type)
 			continue;
@@ -163,6 +169,8 @@ static void dev_exception_clean(struct d
 {
 	struct dev_exception_item *ex, *tmp;
 
+	lockdep_assert_held(&devcgroup_mutex);
+
 	list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
 		list_del_rcu(&ex->list);
 		kfree_rcu(ex, rcu);
@@ -298,6 +306,10 @@ static int may_access(struct dev_cgroup
 	struct dev_exception_item *ex;
 	bool match = false;
 
+	rcu_lockdep_assert(rcu_read_lock_held() ||
+			   lockdep_is_held(&devcgroup_mutex),
+			   "device_cgroup::may_access() called without proper synchronization");
+
 	list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
 		if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
 			continue;


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