ANDROID: rust_binder: adjust errors from death notifications

Rust Binder currently returns an error when death notifications are
registered or removed illegally. This causes tests that use the kernel
interface incorrectly to fail. To have the same behavior as C Binder,
adjust the death notification logic to print but otherwise ignore these
error conditions.

Bug: 430659969
Change-Id: Ia11aebea74ae1441fc48e40cbf43fae56bf3be54
Signed-off-by: Alice Ryhl <aliceryhl@google.com>

drivers/android/binder/process.rs

@@ -1178,20 +1178,20 @@ impl Process {
         let handle: u32 = reader.read()?;
         let cookie: u64 = reader.read()?;
 
-        // TODO: First two should result in error, but not the others.
-
-        // TODO: Do we care about the context manager dying?
-
         // Queue BR_ERROR if we can't allocate memory for the death notification.
         let death = UniqueArc::new_uninit(GFP_KERNEL).map_err(|err| {
             thread.push_return_work(BR_ERROR);
             err
         })?;
         let mut refs = self.node_refs.lock();
-        let info = refs.by_handle.get_mut(&handle).ok_or(EINVAL)?;
+        let Some(info) = refs.by_handle.get_mut(&handle) else {
+            pr_warn!("BC_REQUEST_DEATH_NOTIFICATION invalid ref {handle}\n");
+            return Ok(());
+        };
 
         // Nothing to do if there is already a death notification request for this handle.
         if info.death().is_some() {
+            pr_warn!("BC_REQUEST_DEATH_NOTIFICATION death notification already set\n");
             return Ok(());
         }
 
@@ -1227,12 +1227,19 @@ impl Process {
         let cookie: u64 = reader.read()?;
 
         let mut refs = self.node_refs.lock();
-        let info = refs.by_handle.get_mut(&handle).ok_or(EINVAL)?;
+        let Some(info) = refs.by_handle.get_mut(&handle) else {
+            pr_warn!("BC_CLEAR_DEATH_NOTIFICATION invalid ref {handle}\n");
+            return Ok(());
+        };
 
-        let death = info.death().take().ok_or(EINVAL)?;
+        let Some(death) = info.death().take() else {
+            pr_warn!("BC_CLEAR_DEATH_NOTIFICATION death notification not active\n");
+            return Ok(());
+        };
         if death.cookie != cookie {
             *info.death() = Some(death);
-            return Err(EINVAL);
+            pr_warn!("BC_CLEAR_DEATH_NOTIFICATION death notification cookie mismatch\n");
+            return Ok(());
         }
 
         // Update state and determine if we need to queue a work item. We only need to do it when