linux-kernel - Re: [PATCH RFC v2] slab: introduce kmalloc

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Date:	Mon, 13 Feb 2012 22:44:46 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Xi Wang <xi.wang@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jesper Juhl <jj@...osbits.net>, Jens Axboe <axboe@...nel.dk>,
	Pekka Enberg <penberg@...nel.org>,
	linux-kernel@...r.kernel.org, Matt Mackall <mpm@...enic.com>,
	David Rientjes <rientjes@...gle.com>
Subject: Re: [PATCH RFC v2] slab: introduce kmalloc_array

On Mon, Feb 13, 2012 at 10:01:42AM -0600, Christoph Lameter wrote:
> Well I think the best is just not do any of this. One can already do
> k[zm]alloc(x * sizeof(struct whatever)). Do x*x for 2 dimensions etc etc.
> No need to change the API.
> 

The point was that there are a bunch of places where we have had
integer overflows caused by doing kmalloc(x * sizeof(struct whatever)).
For kzalloc(x * sizeof(struct whatever)), you just write it like
kcalloc(x, sizeof(struct whatever)) and avoid the overflow, but we
don't have a non-zeroing version of kcalloc() to do that.

Probably once we have the kmalloc_array() and people start using it,
we get a bunch of overflow checking automatically and it's a kernel
hardenning thing.  As well we could remove the duplicative checking
so it's a cleanup.

> If you add these variants then please think
> about the necessity to add other variants (like the kmalloc_node() NUMA
> call) etc in the future.
> 

We don't have a kcalloc_node(), so I don't think this is likely to
be a big issue.

regards,
dan carpenter

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