linux-kernel - Re: SLUB: Return ZERO_SIZE

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Message-ID: <4664F44C.4040206@cs.helsinki.fi>
Date:	Tue, 05 Jun 2007 08:27:40 +0300
From:	Pekka Enberg <penberg@...helsinki.fi>
To:	Christoph Lameter <clameter@....com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, Jeremy Fitzhardinge <jeremy@...p.org>
Subject: Re: SLUB: Return ZERO_SIZE_PTR for kmalloc(0)

Christoph Lameter wrote:
> SLUB: Return ZERO_SIZE_PTR for kmalloc(0) V3
> 
> Instead of returning the smallest available object return ZERO_SIZE_PTR.
> 
> A ZERO_SIZE_PTR can be legitimately used as an object pointer as long
> as it is not deferenced. The dereference of ZERO_SIZE_PTR causes a
> distinctive fault.
> kfree can handle a ZERO_SIZE_PTR in the same way as NULL.

FWIW, I am happy :-). We should add a comment to kmalloc() that we 
return non-unique pointers for zero-length allocations though.

Acked-by: Pekka Enberg <penberg@...helsinki.fi>
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