devscgroup: make white list more compact in some cases
Consider you added a 'c foo:bar r' permission to some cgroup and then (a
bit later) 'c'foo:bar w' for it. After this you'll see the
c foo:bar r
c foo:bar w
lines in a devices.list file.
Another example - consider you added 10 'c foo:bar r' permissions to some
cgroup (e.g. by mistake). After this you'll see 10 c foo:bar r lines in
a list file.
This is weird. This situation also has one more annoying consequence.
Having many items in a white list makes permissions checking slower, sine
it has to walk a longer list.
The proposal is to merge permissions for items, that correspond to the
same device.
Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index f9941a7..baf3488 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -106,7 +106,7 @@
static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
struct dev_whitelist_item *wh)
{
- struct dev_whitelist_item *whcopy;
+ struct dev_whitelist_item *whcopy, *walk;
whcopy = kmalloc(sizeof(*whcopy), GFP_KERNEL);
if (!whcopy)
@@ -114,7 +114,21 @@
memcpy(whcopy, wh, sizeof(*whcopy));
spin_lock(&dev_cgroup->lock);
- list_add_tail(&whcopy->list, &dev_cgroup->whitelist);
+ list_for_each_entry(walk, &dev_cgroup->whitelist, list) {
+ if (walk->type != wh->type)
+ continue;
+ if (walk->major != wh->major)
+ continue;
+ if (walk->minor != wh->minor)
+ continue;
+
+ walk->access |= wh->access;
+ kfree(whcopy);
+ whcopy = NULL;
+ }
+
+ if (whcopy != NULL)
+ list_add_tail(&whcopy->list, &dev_cgroup->whitelist);
spin_unlock(&dev_cgroup->lock);
return 0;
}