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

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Message-ID: <20090213142114.GA24047@elte.hu>
Date:	Fri, 13 Feb 2009 15:21:14 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	David Howells <dhowells@...hat.com>
Cc:	torvalds@...l.org, jmorris@...ei.sys, akpm@...ux-foundation.org,
	serue@...ibm.com, kosaki.motohiro@...fujitsu.com,
	linux-kernel@...r.kernel.org, vegard.nossum@...il.com,
	containers@...ts.osdl.org, snakebyte@....de,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [PATCH] User namespaces: Only put the userns when we unhash
	the uid


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

> From: Serge E. Hallyn <serue@...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@...fujitsu.com>
> Signed-off-by: Serge E. Hallyn <serue@...ibm.com>
> Acked-by: David Howells <dhowells@...hat.com>
> Tested-by: Ingo Molnar <mingo@...e.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@...e.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@...hat.com>

	Ingo
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