linux-kernel - Re: [PATCH] rust: implement ForeignOwnable for Pin<Box<T>>

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: <5c49f604-34c1-414f-bf9a-92837c6e07b3@proton.me>
Date: Tue, 30 Jul 2024 17:14:39 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Alice Ryhl <aliceryhl@...gle.com>, Miguel Ojeda <ojeda@...nel.org>
Cc: Alex Gaynor <alex.gaynor@...il.com>, Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Andreas Hindborg <a.hindborg@...sung.com>, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] rust: implement ForeignOwnable for Pin<Box<T>>

On 30.07.24 15:06, Alice Ryhl wrote:
> @@ -89,6 +90,32 @@ unsafe fn from_foreign(ptr: *const core::ffi::c_void) -> Self {
>      }
>  }
> 
> +impl<T: 'static> ForeignOwnable for Pin<Box<T>> {
> +    type Borrowed<'a> = Pin<&'a T>;
> +
> +    fn into_foreign(self) -> *const core::ffi::c_void {
> +        // SAFETY: We are still treating the box as pinned.

I don't think that we have the guarantee that the pointee at the pointer
that is returned by `into_foreign` is not moved.
AFAIU `ForeignOwnable` is used to store these pointers in C structures
and never to actually access the value behind the returned pointer. So
we could add the requirement to `into_foreign` (thus making it `unsafe`)
that the pointer should not be dereferenced/used aside from `borrow` and
`from_foreign`. Otherwise I don't see how the call below can be OK.
What do you think?

---
Cheers,
Benno

> +        Box::into_raw(unsafe { Pin::into_inner_unchecked(self) }) as _
> +    }