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rust: device: fix device context of Device::parent()

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commit cfec502b3d091ff7c24df6ccf8079470584315a0 upstream.

Regardless of the DeviceContext of a device, we can't give any
guarantees about the DeviceContext of its parent device.

This is very subtle, since it's only caused by a simple typo, i.e.

	 Self::from_raw(parent)

which preserves the DeviceContext in this case, vs.

	 Device::from_raw(parent)

which discards the DeviceContext.

(I should have noticed it doing the correct thing in auxiliary::Device
subsequently, but somehow missed it.)

Hence, fix both Device::parent() and auxiliary::Device::parent().

Cc: stable@vger.kernel.org
Fixes: a4c9f71e34 ("rust: device: implement Device::parent()")
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Danilo Krummrich
2025-10-16 15:31:44 +02:00
committed by Greg Kroah-Hartman
parent d3c352207f
commit 2b55b5be1d
2 changed files with 3 additions and 9 deletions
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8
rust/kernel/auxiliary.rs
View File

@@ -217,13 +217,7 @@ impl<Ctx: device::DeviceContext> Device<Ctx> {
/// Returns a reference to the parent [`device::Device`], if any. /// Returns a reference to the parent [`device::Device`], if any.
pub fn parent(&self) -> Option<&device::Device> { pub fn parent(&self) -> Option<&device::Device> {
let ptr: *const Self = self; self.as_ref().parent()
// CAST: `Device<Ctx: DeviceContext>` types are transparent to each other.
let ptr: *const Device = ptr.cast();
// SAFETY: `ptr` was derived from `&self`.
let this = unsafe { &*ptr };
this.as_ref().parent()
} }
} }

4
rust/kernel/device.rs
View File

@@ -250,7 +250,7 @@ impl<Ctx: DeviceContext> Device<Ctx> {
/// Returns a reference to the parent device, if any. /// Returns a reference to the parent device, if any.
#[cfg_attr(not(CONFIG_AUXILIARY_BUS), expect(dead_code))] #[cfg_attr(not(CONFIG_AUXILIARY_BUS), expect(dead_code))]
pub(crate) fn parent(&self) -> Option<&Self> { pub(crate) fn parent(&self) -> Option<&Device> {
// SAFETY: // SAFETY:
// - By the type invariant `self.as_raw()` is always valid. // - By the type invariant `self.as_raw()` is always valid.
// - The parent device is only ever set at device creation. // - The parent device is only ever set at device creation.
@@ -263,7 +263,7 @@ impl<Ctx: DeviceContext> Device<Ctx> {
// - Since `parent` is not NULL, it must be a valid pointer to a `struct device`. // - Since `parent` is not NULL, it must be a valid pointer to a `struct device`.
// - `parent` is valid for the lifetime of `self`, since a `struct device` holds a // - `parent` is valid for the lifetime of `self`, since a `struct device` holds a
// reference count of its parent. // reference count of its parent.
Some(unsafe { Self::from_raw(parent) }) Some(unsafe { Device::from_raw(parent) })
} }
} }