Date: Mon, 13 Feb 2012 22:44:46 +0300
From: Dan Carpenter <dan.carpenter@oracle.com>
To: Christoph Lameter <cl@linux.com>
Cc: Xi Wang <xi.wang@gmail.com>, Andrew Morton <akpm@linux-foundation.org>,
        Jesper Juhl <jj@chaosbits.net>, Jens Axboe <axboe@kernel.dk>,
        Pekka Enberg <penberg@kernel.org>, linux-kernel@vger.kernel.org,
        Matt Mackall <mpm@selenic.com>, David Rientjes <rientjes@google.com>
Subject: Re: [PATCH RFC v2] slab: introduce kmalloc_array
Message-ID: <20120213194446.GD26353@mwanda>
References: <20120208142513.4db2493a.akpm@linux-foundation.org>
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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.
>=20

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.
>=20

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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