linux-kernel - Re: [PATCH v3 09/10] rust: list: support heterogeneous lists

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: <CAH5fLghdOYt-an=Scic4g4tYvU8WMdvwqt4nHP0j8QybaPPp6w@mail.gmail.com>
Date: Thu, 1 Aug 2024 14:33:17 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Miguel Ojeda <ojeda@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, 
	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>, Marco Elver <elver@...gle.com>, Coly Li <colyli@...e.de>, 
	Paolo Abeni <pabeni@...hat.com>, Pierre Gondois <pierre.gondois@....com>, 
	Ingo Molnar <mingo@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Wei Yang <richard.weiyang@...il.com>, 
	Matthew Wilcox <willy@...radead.org>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, Kees Cook <kees@...nel.org>
Subject: Re: [PATCH v3 09/10] rust: list: support heterogeneous lists

On Thu, Aug 1, 2024 at 12:50 PM Benno Lossin <benno.lossin@...ton.me> wrote:
>
> On 01.08.24 11:38, Alice Ryhl wrote:
> > On Thu, Aug 1, 2024 at 11:24 AM Benno Lossin <benno.lossin@...ton.me> wrote:
> >>
> >> On 23.07.24 10:22, Alice Ryhl wrote:
> >>> @@ -181,6 +185,47 @@ unsafe fn from_fields(me: *mut ListLinksFields) -> *mut Self {
> >>>      }
> >>>  }
> >>>
> >>> +/// Similar to [`ListLinks`], but also contains a pointer to the full value.
> >>> +///
> >>> +/// This type can be used instead of [`ListLinks`] to support lists with trait objects.
> >>> +#[repr(C)]
> >>> +pub struct ListLinksSelfPtr<T: ?Sized, const ID: u64 = 0> {
> >>> +    /// The `ListLinks` field inside this value.
> >>> +    ///
> >>> +    /// This is public so that it can be used with `impl_has_list_links!`.
> >>> +    pub inner: ListLinks<ID>,
> >>> +    self_ptr: UnsafeCell<MaybeUninit<*const T>>,
> >>
> >> Why do you need `MaybeUninit`?
> >
> > Right now the constructor initializes it to MaybeUninit::zeroed().
> > What would you initialize it to without MaybeUninit? Remember that the
> > vtable pointer in a fat pointer has strict validity requirements.
>
> Oh... I forgot about that, can you add a comment about that? Also why
> not use `Opaque` in that case then?

It used to just be UnsafeCell, but then I tried it in miri and found
out about the issue and added MaybeUninit. But I can make it use
Opaque instead.

Alice