On Mon, Dec 03, 2012 at 02:31:52PM +0000, Ben Hutchings wrote:
> 3.2-stable review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Tejun Heo <t...@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 <t...@kernel.org>
> Acked-by: Serge E. Hallyn <serge.hal...@ubuntu.com>
> Cc: Aristeu Rozanski <a...@redhat.com>
> Cc: Li Zefan <lize...@huawei.com>
> [bwh: Backported to 3.2:
> - Adjust context
> - Exception list is called whitelist]
> Signed-off-by: Ben Hutchings <b...@decadent.org.uk>
I belive this backport is uneeded for 3.2 (or any stable <= 3.6), since
may_access_whitelist (may_access now in mainline) isn't called under
rcu_read_lock.
> ---
> 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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