device_cgroup: fix RCU usage
dev_cgroup->exceptions is protected with devcgroup_mutex for writes
and RCU for reads; however, RCU usage isn't correct.
* dev_exception_clean() doesn't use RCU variant of list_del() and
kfree(). The function can race with may_access() and may_access()
may end up dereferencing already freed memory. Use list_del_rcu()
and kfree_rcu() instead.
* may_access() may be called only with RCU read locked but doesn't use
RCU safe traversal over ->exceptions. Use list_for_each_entry_rcu().
Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Serge E. Hallyn <serge.hallyn@ubuntu.com>
Cc: stable@vger.kernel.org
Cc: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 96d87ea..b08d20c 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -164,8 +164,8 @@
struct dev_exception_item *ex, *tmp;
list_for_each_entry_safe(ex, tmp, &dev_cgroup->exceptions, list) {
- list_del(&ex->list);
- kfree(ex);
+ list_del_rcu(&ex->list);
+ kfree_rcu(ex, rcu);
}
}
@@ -298,7 +298,7 @@
struct dev_exception_item *ex;
bool match = false;
- list_for_each_entry(ex, &dev_cgroup->exceptions, list) {
+ list_for_each_entry_rcu(ex, &dev_cgroup->exceptions, list) {
if ((refex->type & DEV_BLOCK) && !(ex->type & DEV_BLOCK))
continue;
if ((refex->type & DEV_CHAR) && !(ex->type & DEV_CHAR))