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: a4c9f71e3440 ("rust: device: implement Device::parent()") Signed-off-by: Danilo Krummrich dakr@kernel.org --- rust/kernel/auxiliary.rs | 8 +------- rust/kernel/device.rs | 4 ++-- 2 files changed, 3 insertions(+), 9 deletions(-)

diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs index 4163129b4103..e12f78734606 100644 --- a/rust/kernel/auxiliary.rs +++ b/rust/kernel/auxiliary.rs @@ -217,13 +217,7 @@ pub fn id(&self) -> u32 {

/// Returns a reference to the parent [`device::Device`], if any. pub fn parent(&self) -> Option<&device::Device> { - let ptr: *const Self = self; - // 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() + self.as_ref().parent() } }

diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs index 23a95324cb0f..343996027c89 100644 --- a/rust/kernel/device.rs +++ b/rust/kernel/device.rs @@ -256,7 +256,7 @@ pub(crate) fn as_raw(&self) -> *mut bindings::device {

/// Returns a reference to the parent device, if any. #[cfg_attr(not(CONFIG_AUXILIARY_BUS), expect(dead_code))] - pub(crate) fn parent(&self) -> Option<&Self> { + pub(crate) fn parent(&self) -> Option<&Device> { // SAFETY: // - By the type invariant `self.as_raw()` is always valid. // - The parent device is only ever set at device creation. @@ -269,7 +269,7 @@ pub(crate) fn parent(&self) -> Option<&Self> { // - 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 // reference count of its parent. - Some(unsafe { Self::from_raw(parent) }) + Some(unsafe { Device::from_raw(parent) }) } }