rust: drm: gem: clean up GEM state in init failure case

commit 2e42a17 upstream.

Currently, if `drm_gem_object_init` fails, the object is freed without
any cleanup. Perform the cleanup in that case.

Cc: stable@vger.kernel.org
Fixes: c284d3e ("rust: drm: gem: Add GEM object abstraction")
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Onur Özkan <work@onurozkan.dev>
Link: https://patch.msgid.link/20260423-fix-gem-1-v1-1-e12e35f7bba9@nvidia.com
[ Move safety comment closer to unsafe block to avoid a clippy warning.
  - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Eliot Courtney

rust/kernel/drm/gem/mod.rs

@@ -232,8 +232,17 @@ impl<T: DriverObject> Object<T> {
         // SAFETY: `obj.as_raw()` is guaranteed to be valid by the initialization above.
         unsafe { (*obj.as_raw()).funcs = &Self::OBJECT_FUNCS };
 
-        // SAFETY: The arguments are all valid per the type invariants.
-        to_result(unsafe { bindings::drm_gem_object_init(dev.as_raw(), obj.obj.get(), size) })?;
+        if let Err(err) =
+            // SAFETY: The arguments are all valid per the type invariants.
+            to_result(unsafe {
+                bindings::drm_gem_object_init(dev.as_raw(), obj.obj.get(), size)
+            })
+        {
+            // SAFETY: `drm_gem_object_init()` initializes the private GEM object state before
+            // failing, so `drm_gem_private_object_fini()` is the matching cleanup.
+            unsafe { bindings::drm_gem_private_object_fini(obj.obj.get()) };
+            return Err(err);
+        }
 
         // SAFETY: We never move out of `Self`.
         let ptr = KBox::into_raw(unsafe { Pin::into_inner_unchecked(obj) });