linux-kernel - Re: [PATCH 2/2] cgroup: if you list_empty() a head then don't list

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Message-ID: <20110315163523.GB12170@shutemov.name>
Date:	Tue, 15 Mar 2011 18:35:23 +0200
From:	"Kirill A. Shutemov" <kirill@...temov.name>
To:	Phil Carmody <ext-phil.2.carmody@...ia.com>
Cc:	menage@...gle.com, lizf@...fujitsu.com,
	containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Subject: Re: [PATCH 2/2] cgroup: if you list_empty() a head then don't
 list_del() it

On Tue, Mar 15, 2011 at 03:08:43PM +0200, Phil Carmody wrote:
> list_del() leaves poison in the prev and next pointers. The next
> list_empty() will compare those poisons, and say the list isn't empty.
> Any list operations that assume the node is on a list because of such a
> check will be fooled into dereferencing poison. One needs to INIT the
> node after the del, and fortunately there's already a wrapper for that -
> list_del_init().
> 
> Some of the dels are followed by deallocations, so can be ignored,
> and one can be merged with an add to make a move. Apart from that, I
> erred on the side of caution in making nodes list_empty()-queriable.
> 
> Signed-off-by: Phil Carmody <ext-phil.2.carmody@...ia.com>

Acked-by: Kirill A. Shutemov <kirill@...temov.name>

-- 
 Kirill A. Shutemov
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