Commit cfec502b authored by Danilo Krummrich's avatar Danilo Krummrich
Browse files

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



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: a4c9f71e ("rust: device: implement Device::parent()")
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Acked-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
parent c7fbb821

rust/kernel/auxiliary.rs

+1 −7
Original line number Diff line number Diff line
@@ -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()

    }

}

rust/kernel/device.rs

+2 −2
Original line number Diff line number Diff line
@@ -251,7 +251,7 @@ 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.
@@ -264,7 +264,7 @@ 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) })

        }

    }