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From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Thu, 15 Apr 2021 14:39:58 +0200
Message-ID: <CANiq72=miTm-WYN4Q4JRfm7ocaoNePW_f1khcUOE1EkO8UyQzw@mail.gmail.com>
Subject: Re: [PATCH 00/13] [RFC] Rust support
To:     Kees Cook <keescook@chromium.org>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
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On Thu, Apr 15, 2021 at 3:38 AM Kees Cook <keescook@chromium.org> wrote:
>
> Before anything else: yay! I'm really glad to see this RFC officially
> hit LKML. :)

Thanks! :)

> When originally learning Rust I was disappointed to see that (by default)
> Rust similarly ignores the overflow problem, but I'm glad to see the
> very intentional choices in the Rust-in-Linux design to deal with it
> directly. I think the default behavior should be saturate-with-WARN
> (this will match the ultimate goals of the UBSAN overflow support[1][2]
> in the C portions of the kernel). Rust code wanting wrapping/checking
> can expressly use those. The list of exploitable overflows is loooong,
> and this will remain a weakness in Rust unless we get it right from
> the start. What's not clear to me is if it's better to say "math with
> undeclared overflow expectation" will saturate" or to say "all math must
> declare its overflow expectation".

+1 Agreed, we need to get this right (and ideally make both the C and
Rust sides agree...).

Cheers,
Miguel