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@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
Cc: Aristeu Rozanski <aris@xxxxxxxxxx>
Cc: Li Zefan <lizefan@xxxxxxxxxx>
Cc: Serge E. Hallyn <serge.hallyn@xxxxxxxxxx>
---
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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