linux-kernel - Re: [PATCH v2 1/4] rust: device: implement Device::parent()

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 for Android: free password hash cracker in your pocket

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

Message-ID: <Z916eZ1_Jd3VQz3Y@Mac.home>
Date: Fri, 21 Mar 2025 07:40:57 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: bhelgaas@...gle.com, gregkh@...uxfoundation.org, rafael@...nel.org,
	ojeda@...nel.org, alex.gaynor@...il.com, gary@...yguo.net,
	bjorn3_gh@...tonmail.com, benno.lossin@...ton.me,
	a.hindborg@...nel.org, aliceryhl@...gle.com, tmgross@...ch.edu,
	linux-pci@...r.kernel.org, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] rust: device: implement Device::parent()

On Thu, Mar 20, 2025 at 11:27:43PM +0100, Danilo Krummrich wrote:
> Device::parent() returns a reference to the device' parent device, if
> any.
> 
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
> ---
>  rust/kernel/device.rs | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
> 
> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> index 21b343a1dc4d..f6bdc2646028 100644
> --- a/rust/kernel/device.rs
> +++ b/rust/kernel/device.rs
> @@ -65,6 +65,21 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {
>          self.0.get()
>      }
>  
> +    /// Returns a reference to the parent device, if any.
> +    pub fn parent<'a>(&self) -> Option<&'a Self> {
> +        // SAFETY:
> +        // - By the type invariant `self.as_raw()` is always valid.
> +        // - The parent device is only ever set at device creation.
> +        let parent = unsafe { (*self.as_raw()).parent };
> +
> +        if parent.is_null() {
> +            None
> +        } else {
> +            // SAFETY: Since `parent` is not NULL, it must be a valid pointer to a `struct device`.
> +            Some(unsafe { Self::as_ref(parent) })

The safety comment also needs to explain why the parent device won't be
gone, I assume a struct device holds a refcount of its parent? Therefore
the borrow checker would ensure the parent exists as long as the Device
is borrowed.

Regards,
Boqun

> +        }
> +    }
> +
>      /// Convert a raw C `struct device` pointer to a `&'a Device`.
>      ///
>      /// # Safety
> -- 
> 2.48.1
>