From c5ee58688baa98bc3a4f6095a1acf6fd7fd9e967 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Tue, 6 Nov 2012 09:17:37 -0800 Subject: [PATCH] device_cgroup: fix RCU usage 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 Acked-by: Serge E. Hallyn Cc: Aristeu Rozanski Cc: Li Zefan [bwh: Backported to 3.2: - Adjust context - Exception list is called whitelist] Signed-off-by: Ben Hutchings --- security/device_cgroup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/security/device_cgroup.c b/security/device_cgroup.c index 4450fbeec411..92e24bb6443e 100644 --- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -202,8 +202,8 @@ static void devcgroup_destroy(struct cgroup_subsys *ss, 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); } @@ -278,7 +278,7 @@ static int may_access_whitelist(struct dev_cgroup *c, { 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)) -- 2.39.2