[PATCH] cgroups: fix possible use after free

[Paul Menage]

On Tue, Feb 10, 2009 at 5:19 PM, Al Viro <viro at zeniv.linux.org.uk> wrote:
>
> So you can't wrap sget() into a mutex that might be grabbed at some
> point of ->kill_sb() or it'll wait forever in that scenario.

Good point.

>
> So no exclusion is needed there at all.  If you don't want later remount
> of the first mount to affect these flags of second one you shouldn't share
> the superblock at all, obviously...

I have plans for some slightly more complex state in that structure -
I'll probably just add a spinlock around accesses to those fields so
that we can avoid exposing any inconsistent state.

Paul