linux-kernel - Re: [PATCH v9 06/27] rust: add C helpers

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Date:   Wed, 17 Aug 2022 13:34:20 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
Cc:     Miguel Ojeda <ojeda@...nel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, patches@...ts.linux.dev,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Geoffrey Thomas <geofft@...reload.com>,
        Wedson Almeida Filho <wedsonaf@...gle.com>,
        Sven Van Asbroeck <thesven73@...il.com>,
        Gary Guo <gary@...yguo.net>, Boqun Feng <boqun.feng@...il.com>,
        Maciej Falkowski <m.falkowski@...sung.com>,
        Wei Liu <wei.liu@...nel.org>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>
Subject: Re: [PATCH v9 06/27] rust: add C helpers

On Wed, Aug 17, 2022 at 10:22:37PM +0200, Miguel Ojeda wrote:
> On Wed, Aug 17, 2022 at 9:44 PM Kees Cook <keescook@...omium.org> wrote:
> > Given the distaste for ever using BUG()[1], why does this helper exist?
> 
> We use it exclusively for the Rust panic handler, which does not
> return (we use fallible operations as much as possible, of course, but
> we need to provide a panic handler nevertheless).

Gotcha -- it's for the implicit situations (e.g. -C overflow-checks=on),
nothing is expected to explicitly call the Rust panic handler?

> Killing the entire machine is definitely too aggressive for some
> setups/situations, so at some point last year we discussed potential
> alternatives (e.g. `make_task_dead()` or similar) with, if I recall
> correctly, Greg. Maybe we want to make it configurable too. We are
> open to suggestions!

I suffer the same problems trying to fix C and the old "can never fail"
interfaces. Mainly we've just been systematically replacing such APIs
with APIs that return error codes, allowing the error to bubble back up.
(Which I know is exactly what you've already done with the allocator,
etc. Yay!)

-Kees

-- 
Kees Cook