linux-hardening - Re: [PATCH 1/2] overflow: Implement size

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Message-ID: <CAKwvOdk+S=sTJWePADwrHFbVKKW1-WijzcS898GU2B0h57vt3Q@mail.gmail.com>
Date:   Mon, 24 Jan 2022 13:16:51 -0800
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        "Gustavo A . R . Silva" <gustavoars@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Leon Romanovsky <leon@...nel.org>,
        Keith Busch <kbusch@...nel.org>, Len Baker <len.baker@....com>,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 1/2] overflow: Implement size_t saturating arithmetic helpers

On Mon, Jan 24, 2022 at 1:13 PM Kees Cook <keescook@...omium.org> wrote:
>
> What I'd really like is a "store this in a size_t" check to catch dumb
> storage size problems (or related overflows). In other words:
>
> size_t big1 = 2147483647;
> size_t big2 = 2147483647;
>
> /* Doesn't overflow, but 4611686014132420609 becomes a 1 for int */
> int size = size_mul(big1, big2);
> ...
> ptr = kmalloc(size, GFP_KERNEL); /* Allocates a 1 instead... */

-Wshorten-64-to-32
?

-- 
Thanks,
~Nick Desaulniers