linux-kernel - Re: [PATCH] uaccess: rust: add strncpy_from

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CANiq72=VbcYroRz1EcbzHqFHwaHLewK+DvK756ropM16pDdMuw@mail.gmail.com>
Date: Thu, 24 Apr 2025 18:38:52 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, rust-for-linux@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] uaccess: rust: add strncpy_from_user

On Thu, Apr 24, 2025 at 5:18 PM Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> +    if res < 0 {
> +        Err(Error::from_errno(res as i32))
> +    } else {
> +        #[cfg(CONFIG_RUST_OVERFLOW_CHECKS)]
> +        assert!(res <= len);
> +        Ok(res as usize)
> +    }

What about:

    if res < 0 {
        return Err(...);
    }

    overflow_assert!(res <= len);
    Ok(res as usize)

That follows a bit better what is usually done on the C side, in using
early returns (especially for error paths) and in avoiding local
`#ifdef`s.

Of course, we can leave this `overflow_assert!` to a different patch
later on with this code as an example use case, or a good first issue
etc. It also allows to document it etc. Happy to send it or create the
issue.

(I wrote that instead of `assert_overflow!` because it follows the
`{static,debug}_assert!` patterns, i.e. it changes more the "kind" of
assert rather than asserting a particular thing, like `_eq!` or
`_same_type!`).

Thanks!

Cheers,
Miguel