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devscgroup: make white list more compact in some cases

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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>
This commit is contained in:
Pavel Emelyanov 2008-06-05 22:46:28 -07:00 committed by Linus Torvalds
parent 7db9cfd380
commit d1ee2971f5
1 changed files with 16 additions and 2 deletions
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18
security/device_cgroup.c
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@ -106,7 +106,7 @@ static int dev_whitelist_copy(struct list_head *dest, struct list_head *orig)
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 @@ static int dev_whitelist_add(struct dev_cgroup *dev_cgroup,
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;
}