commit
201e72acb2d3821e2de9ce6091e98859c316b29a upstream.
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: Aristeu Rozanski <aris@redhat.com>
Cc: Li Zefan <lizefan@huawei.com>
[bwh: Backported to 3.2:
- Adjust context
- Exception list is called whitelist]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
dev_cgroup = cgroup_to_devcgroup(cgroup);
list_for_each_entry_safe(wh, tmp, &dev_cgroup->whitelist, list) {
- list_del(&wh->list);
- kfree(wh);
+ list_del_rcu(&wh->list);
+ kfree_rcu(wh, rcu);
}
kfree(dev_cgroup);
}
{
struct dev_whitelist_item *whitem;
- list_for_each_entry(whitem, &c->whitelist, list) {
+ list_for_each_entry_rcu(whitem, &c->whitelist, list) {
if (whitem->type & DEV_ALL)
return 1;
if ((refwh->type & DEV_BLOCK) && !(whitem->type & DEV_BLOCK))