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Date: Sun, 29 Apr 2018 13:30:23 -0700
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 2/2] mm: Add kvmalloc_ab_c and kvzalloc_struct
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To: Kees Cook <keescook@chromium.org>
Cc: Julia Lawall <julia.lawall@lip6.fr>, Andrew Morton <akpm@linux-foundation.org>, Matthew Wilcox <mawilcox@microsoft.com>, Linux-MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>, Kernel Hardening <kernel-hardening@lists.openwall.com>, cocci@systeme.lip6.fr, Himanshu Jha <himanshujha199640@gmail.com>

On Sun, Apr 29, 2018 at 09:59:27AM -0700, Kees Cook wrote:
> Did this ever happen?

Not yet.  I brought it up at LSFMM, and I'll repost the patches soon.

> I'd also like to see kmalloc_array_3d() or
> something that takes three size arguments. We have a lot of this
> pattern too:
> 
> kmalloc(sizeof(foo) * A * B, gfp...)
> 
> And we could turn that into:
> 
> kmalloc_array_3d(sizeof(foo), A, B, gfp...)

Are either of A or B constant?  Because if so, we could just use
kmalloc_array.  If not, then kmalloc_array_3d becomes a little more
expensive than kmalloc_array because we have to do a divide at runtime
instead of compile-time.  that's still better than allocating too few
bytes, of course.

I'm wondering how far down the abc + ab + ac + bc + d rabbit-hole we're
going to end up going.  As far as we have to, I guess.