linux-kernel - Re: [PATCH] fix freeing user

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Date:	Fri, 24 Dec 2010 23:56:25 +0000
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Hillf Danton <dhillf@...il.com>
Cc:	Greg KH <gregkh@...e.de>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fix freeing user_struct in user cache

Quoting Hillf Danton (dhillf@...il.com):
> On Fri, Dec 24, 2010 at 11:55 AM, Greg KH <gregkh@...e.de> wrote:
> > On Thu, Dec 23, 2010 at 08:52:34PM +0800, Hillf Danton wrote:
> >> When racing on adding into user cache, the new allocated from mm slab
> >> is freed without putting user namespace.
> >>
> >> Since the user namespace is already operated by getting, putting has
> >> to be issued.
> >>
> >> btw, it could be freed out of lock?
> >>
> >> Signed-off-by: Hillf Danton <dhillf@...il.com>
> >> ---
> >>
> >> --- a/kernel/user.c   2010-11-01 19:54:12.000000000 +0800
> >> +++ b/kernel/user.c   2010-12-23 20:42:00.000000000 +0800
> >> @@ -158,6 +158,7 @@ struct user_struct *alloc_uid(struct use
> >>               spin_lock_irq(&uidhash_lock);
> >>               up = uid_hash_find(uid, hashent);
> >>               if (up) {
> >> +                     put_user_ns(ns);
> >>                       key_put(new->uid_keyring);
> >>                       key_put(new->session_keyring);
> >>                       kmem_cache_free(uid_cachep, new);
> >
> > Hm, are you sure about this?  Also, why send this to me, did I last
> > touch this?
> >
> 
> sure with no doubt.

Good catch, thanks.

Acked-by: Serge Hallyn <serge@...lyn.com>

> I do not know if you touched that last, but I received the following message,

thanks,
-serge
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