linux-kernel - Re: [PATCH 0/2] Add kvzalloc_struct to complement kvzalloc

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Date:   Wed, 14 Feb 2018 11:32:45 -0800
From:   Joe Perches <joe@...ches.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Matthew Wilcox <willy@...radead.org>,
        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>
Subject: Re: [PATCH 0/2] Add kvzalloc_struct to complement kvzalloc_array

On Wed, 2018-02-14 at 11:23 -0800, Kees Cook wrote:
> On Wed, Feb 14, 2018 at 10:47 AM, Joe Perches <joe@...ches.com> wrote:
> > On Wed, 2018-02-14 at 10:26 -0800, Matthew Wilcox wrote:
> > > From: Matthew Wilcox <mawilcox@...rosoft.com>
> > > 
> > > We all know the perils of multiplying a value provided from userspace
> > > by a constant and then allocating the resulting number of bytes.  That's
> > > why we have kvmalloc_array(), so we don't have to think about it.
> > > This solves the same problem when we embed one of these arrays in a
> > > struct like this:
> > > 
> > > struct {
> > >       int n;
> > >       unsigned long array[];
> > > };
> > 
> > I think expanding the number of allocation functions
> > is not necessary.
> 
> I think removing common mispatterns in favor of overflow-protected
> allocation functions makes sense.

Function symmetry matters too.

These allocation functions are specific to kvz<foo>
and are not symmetric for k<foo>, v<foo>, devm_<foo>
<foo>_node, and the like.