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Date:   Wed, 26 Feb 2020 13:56:56 -0800
From:   Kees Cook <keescook@chromium.org>
To:     Daniel Axtens <dja@axtens.net>
Cc:     Daniel Micay <danielmicay@gmail.com>,
        Kernel Hardening <kernel-hardening@lists.openwall.com>,
        Linux-MM <linux-mm@kvack.org>,
        kernel list <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 5/5] [RFC] mm: annotate memory allocation functions with
 their sizes
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On Wed, Feb 26, 2020 at 05:07:18PM +1100, Daniel Axtens wrote:
> Kees Cook <keescook@chromium.org> writes:
> 
> > On Fri, Feb 07, 2020 at 03:38:22PM -0500, Daniel Micay wrote:
> >> There are some uses of ksize in the kernel making use of the real
> >> usable size of memory allocations rather than only the requested
> >> amount. It's incorrect when mixed with alloc_size markers, since if a
> >> number like 14 is passed that's used as the upper bound, rather than a
> >> rounded size like 16 returned by ksize. It's unlikely to trigger any
> >> issues with only CONFIG_FORTIFY_SOURCE, but it becomes more likely
> >> with -fsanitize=object-size or other library-based usage of
> >> __builtin_object_size.
> >
> > I think the solution here is to use a macro that does the per-bucket
> > rounding and applies them to the attributes. Keep the bucket size lists
> > in sync will likely need some BUILD_BUG_ON()s or similar.
> 
> I can have a go at this but with various other work projects it has
> unfortunately slipped way down the to-do list. So I've very happy for
> anyone else to take this and run with it.

Sounds good. I've added the above note from Micay to the KSPP bug tracker:
https://github.com/KSPP/linux/issues/5

Thanks for bringing this topic back up!

-- 
Kees Cook