linux-kernel - Re: [PATCH v3 08/15] rust: pin-init: add `?Sized` bounds to traits in `#[pin

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Message-Id: <DFOJB99C7PKV.C3LDKTX3MT6O@garyguo.net>
Date: Wed, 14 Jan 2026 18:47:28 +0000
From: "Gary Guo" <gary@...yguo.net>
To: "Benno Lossin" <lossin@...nel.org>, "Gary Guo" <gary@...yguo.net>,
 "Miguel Ojeda" <ojeda@...nel.org>, "Boqun Feng" <boqun.feng@...il.com>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "Danilo Krummrich" <dakr@...nel.org>,
 "Fiona Behrens" <me@...enk.dev>, "Tamir Duberstein" <tamird@...il.com>
Cc: <rust-for-linux@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 08/15] rust: pin-init: add `?Sized` bounds to traits
 in `#[pin_data]` macro

On Wed Jan 14, 2026 at 6:18 PM GMT, Benno Lossin wrote:
> The `#[pin_data]` macro uses some auxiliary traits to ensure that a user
> does not implement `Drop` for the annotated struct, as that is unsound
> and can lead to UB. However, if the struct that is annotated is
> `!Sized`, the current bounds do not work, because `Sized` is an implicit
> bound for generics.
> 
> This is *not* a soundness hole of pin-init, as it currently is
> impossible to construct an unsized struct using pin-init.
> 
> Tested-by: Andreas Hindborg <a.hindborg@...nel.org>
> Signed-off-by: Benno Lossin <lossin@...nel.org>

Reviewed-by: Gary Guo <gary@...yguo.net>

> ---
> Changes in v3: none
> Changes in v2: none
> ---
>  rust/pin-init/internal/src/pin_data.rs | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)