Re: [PATCH] User namespaces: Only put the userns when we unhash the uid

[Ingo Molnar <mingo@elte.hu>]

* David Howells <dhowells@redhat.com> wrote:

> From: Serge E. Hallyn <serue@us.ibm.com>
> 
> uids in namespaces other than init don't get a sysfs entry.
> 
> For those in the init namespace, while we're waiting to remove
> the sysfs entry for the uid the uid is still hashed, and
> alloc_uid() may re-grab that uid without getting a new
> reference to the user_ns, which we've already put in free_user
> before scheduling remove_user_sysfs_dir().
> 
> Reported-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
> Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
> Acked-by: David Howells <dhowells@redhat.com>
> Tested-by: Ingo Molnar <mingo@elte.hu>

beyond the crashes, this should resolve this slab corruption
regression too:

Bug-Entry       : http://bugzilla.kernel.org/show_bug.cgi?id=12503
Subject         : [slab corruption] BUG key_jar: Poison overwritten
Submitter       : Ingo Molnar <mingo@elte.hu>
Date            : 2009-01-15 18:16 (25 days old)
References      : http://marc.info/?l=linux-kernel&m=123204353425825&w=4
Handled-By      : David Howells <dhowells@redhat.com>

	Ingo