linux-kernel - Re: [PATCH] rust: check type of `$ptr` in `container

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: <CAJ-ks9ngPKeoR86WX=qcuS8LtMafZuRXQt7+J9YRv+NVoSgr-A@mail.gmail.com>
Date: Fri, 11 Apr 2025 11:41:57 -0400
From: Tamir Duberstein <tamird@...il.com>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	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] rust: check type of `$ptr` in `container_of!`

On Fri, Apr 11, 2025 at 10:36 AM Alice Ryhl <aliceryhl@...gle.com> wrote:
>
> On Fri, Apr 11, 2025 at 4:31 PM Tamir Duberstein <tamird@...il.com> wrote:
> >
> > Add a compile-time check that `*$ptr` is of the type of `$type->$($f)*`.
> >
> > Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
> > Link: https://lore.kernel.org/all/CAH5fLgh6gmqGBhPMi2SKn7mCmMWfOSiS0WP5wBuGPYh9ZTAiww@mail.gmail.com/
> > Signed-off-by: Tamir Duberstein <tamird@...il.com>
> > ---
> >  rust/kernel/lib.rs | 5 ++++-
> >  1 file changed, 4 insertions(+), 1 deletion(-)
> >
> > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> > index 1df11156302a..da9e36aa7967 100644
> > --- a/rust/kernel/lib.rs
> > +++ b/rust/kernel/lib.rs
> > @@ -200,7 +200,10 @@ fn panic(info: &core::panic::PanicInfo<'_>) -> ! {
> >  macro_rules! container_of {
> >      ($ptr:expr, $type:ty, $($f:tt)*) => {{
> >          let offset: usize = ::core::mem::offset_of!($type, $($f)*);
> > -        $ptr.byte_sub(offset).cast::<$type>()
> > +        let container = $ptr.byte_sub(offset).cast::<$type>();
> > +        fn assert_same_type<T>(_: T, _: T) {}
> > +        assert_same_type($ptr, ::core::mem::addr_of!((*container).$($f)*).cast_mut());

I noticed I accidentally sent `::core::mem::addr_of` instead of
`::core::ptr::addr_of`; will fix once we agree below.

> Perhaps it would be better to wrap the type check in an `if false` to
> avoid evaluating the expressions at runtime?

It's optimized out at O1: https://godbolt.org/z/44Go5xnWr. Is it worth it?