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From:   Daniel Axtens <dja@axtens.net>
To:     Kees Cook <keescook@chromium.org>,
        Daniel Micay <danielmicay@gmail.com>
Cc:     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
In-Reply-To: <202002251035.AD29F84@keescook>
References: <20200120074344.504-1-dja@axtens.net> <20200120074344.504-6-dja@axtens.net> <CA+DvKQJ6jRHZeZteqY7q-9sU8v3xacSPj65uac3PQfst4cKiMA@mail.gmail.com> <202002251035.AD29F84@keescook>
Date:   Wed, 26 Feb 2020 17:07:18 +1100
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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.

Regards,
Daniel

>
> -- 
> Kees Cook