linux-kernel - Re: [PATCH 5/5] [RFC] mm: annotate memory allocation functions with their sizes

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Message-ID: <87wo89rieh.fsf@dja-thinkpad.axtens.net>
Date:   Wed, 26 Feb 2020 17:07:18 +1100
From:   Daniel Axtens <dja@...ens.net>
To:     Kees Cook <keescook@...omium.org>,
        Daniel Micay <danielmicay@...il.com>
Cc:     Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        Linux-MM <linux-mm@...ck.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 5/5] [RFC] mm: annotate memory allocation functions with their sizes

Kees Cook <keescook@...omium.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