rust_binder: clear freeze listener on node removal

Generally userspace is supposed to explicitly clear freeze listeners
before they drop the refcount on the node ref to zero, but there's
nothing forcing that. Currently, in this scenario the freeze listener
remains in the freeze_listeners rbtree and in the remote node's freeze
listener list, even though the ref for which the listener is registered
is gone. This could potentially lead to a memory leak due to a refcount
cycle. Thus, remove the freeze listener in this scenario.

Cc: stable <stable@kernel.org>
Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Link: https://patch.msgid.link/20260703-remove-freeze-on-remove-node-v3-1-6e0c4547af46@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/android/binder/node.rs b/drivers/android/binder/node.rs
index 69f757ff7461..c10148e9069f 100644
--- a/drivers/android/binder/node.rs
+++ b/drivers/android/binder/node.rs
@@ -682,12 +682,13 @@ impl Node {
         }
     }
 
-    pub(crate) fn remove_freeze_listener(&self, p: &Arc<Process>) {
-        let _unused_capacity;
+    pub(crate) fn remove_freeze_listener(&self, p: &Process) -> KVVec<Arc<Process>> {
         let mut guard = self.owner.inner.lock();
         let inner = self.inner.access_mut(&mut guard);
         let len = inner.freeze_list.len();
-        inner.freeze_list.retain(|proc| !Arc::ptr_eq(proc, p));
+        inner
+            .freeze_list
+            .retain(|proc| !core::ptr::eq::<Process>(&**proc, p));
         if len == inner.freeze_list.len() {
             pr_warn!(
                 "Could not remove freeze listener for {}\n",
@@ -695,8 +696,9 @@ impl Node {
             );
         }
         if inner.freeze_list.is_empty() {
-            _unused_capacity = mem::take(&mut inner.freeze_list);
+            return mem::take(&mut inner.freeze_list);
         }
+        KVVec::new()
     }
 
     pub(crate) fn freeze_list<'a>(&'a self, guard: &'a ProcessInner) -> &'a [Arc<Process>] {