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 <20210920180853.1825195-2-keescook@chromium.org> <aa42ebfa-03b8-93fa-e036-a7507397d0dc@rasmusvillemoes.dk>
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From:   Nick Desaulniers <ndesaulniers@google.com>
Date:   Mon, 24 Jan 2022 13:16:51 -0800
Message-ID: <CAKwvOdk+S=sTJWePADwrHFbVKKW1-WijzcS898GU2B0h57vt3Q@mail.gmail.com>
Subject: Re: [PATCH 1/2] overflow: Implement size_t saturating arithmetic helpers
To:     Kees Cook <keescook@chromium.org>
Cc:     Rasmus Villemoes <linux@rasmusvillemoes.dk>,
        "Gustavo A . R . Silva" <gustavoars@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Jason Gunthorpe <jgg@ziepe.ca>,
        Leon Romanovsky <leon@kernel.org>,
        Keith Busch <kbusch@kernel.org>, Len Baker <len.baker@gmx.com>,
        linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
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On Mon, Jan 24, 2022 at 1:13 PM Kees Cook <keescook@chromium.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