linux-kernel - Re: [PATCH 2/2] mm: Add kvmalloc_ab_c and kvzalloc

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Date:   Sun, 29 Apr 2018 13:30:23 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     Julia Lawall <julia.lawall@...6.fr>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Matthew Wilcox <mawilcox@...rosoft.com>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        cocci@...teme.lip6.fr, Himanshu Jha <himanshujha199640@...il.com>
Subject: Re: [PATCH 2/2] mm: Add kvmalloc_ab_c and kvzalloc_struct

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.