| Date | Mon, 03 Dec 2012 14:31:52 +0000 | From | Ben Hutchings <> | Subject | [ 06/89] device_cgroup: fix RCU usage |
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3.2-stable review patch. If anyone has any objections, please let me know.
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From: Tejun Heo <tj@kernel.org>
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> --- security/device_cgroup.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
--- a/security/device_cgroup.c +++ b/security/device_cgroup.c @@ -202,8 +202,8 @@ static void devcgroup_destroy(struct cgr 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 d { 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))
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