device_cgroup: add lockdep asserts

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@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index b08d20c66c2e..78a16f5b7275 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -82,6 +82,8 @@ static int dev_exceptions_copy(struct list_head *dest, struct list_head *orig)
 {
         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_cgroup *dev_cgroup,
 {
         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_cgroup *dev_cgroup,
 {
         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 dev_cgroup *dev_cgroup)
 {
         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 *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;