Commit 2e9fdbe5 authored by Danilo Krummrich's avatar Danilo Krummrich
Browse files

rust: drm: device: drop_in_place() the drm::Device in release() 



In drm::Device::new() we allocate with __drm_dev_alloc() and return an
ARef<drm::Device>.

When the reference count of the drm::Device falls to zero, the C code
automatically calls drm_dev_release(), which eventually frees the memory
allocated in drm::Device::new().

However, due to that, drm::Device::drop() is never called. As a result
the destructor of the user's private data, i.e. drm::Device::data is
never called. Hence, fix this by calling drop_in_place() from the DRM
device's release callback.

Fixes: 1e4b8896 ("rust: drm: add device abstraction")
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Signed-off-by: default avatarDanilo Krummrich <dakr@kernel.org>
Link: https://lore.kernel.org/r/20250629153747.72536-1-dakr@kernel.org
parent e79d0ba6

rust/kernel/drm/device.rs

+11 −1
Original line number Diff line number Diff line
@@ -66,7 +66,7 @@ impl<T: drm::Driver> Device<T> { 
        open: Some(drm::File::<T::File>::open_callback),

        postclose: Some(drm::File::<T::File>::postclose_callback),

        unload: None,

        release: None,

        release: Some(Self::release),

        master_set: None,

        master_drop: None,

        debugfs_init: None,
@@ -162,6 +162,16 @@ pub unsafe fn as_ref<'a>(ptr: *const bindings::drm_device) -> &'a Self { 
        // SAFETY: `ptr` is valid by the safety requirements of this function.

        unsafe { &*ptr.cast() }

    }



    extern "C" fn release(ptr: *mut bindings::drm_device) {

        // SAFETY: `ptr` is a valid pointer to a `struct drm_device` and embedded in `Self`.

        let this = unsafe { Self::from_drm_device(ptr) };



        // SAFETY:

        // - When `release` runs it is guaranteed that there is no further access to `this`.

        // - `this` is valid for dropping.

        unsafe { core::ptr::drop_in_place(this) };

    }

}



impl<T: drm::Driver> Deref for Device<T> {