[PATCH v2] rust_binder: reject context manager self-transaction

[Keshav Verma <iganschel@gmail.com>]

Rust binder resolved handle 0 to the context manager node, but it does not
reject the case where the caller owns the same node.

The C binder driver rejects transactions from the context-manager process
to handle 0 after resolving the target node. Match that behavior in Rust
Binder by rejecting handle 0 transactions when the resolved context-manager
node is owned by the calling process.

This applies to both synchronous and oneway transactions because both paths
resolve the target through Process::get_transaction_node().

Cc: stable@kernel.org
Fixes: eafedbc7c050 ("rust_binder: add Rust Binder driver")
Signed-off-by: Keshav Verma <iganschel@gmail.com>
---
Changes in v2:
- Compare the underlying OS process task instead of Rust Binder `Process` object.

 drivers/android/binder/process.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/android/binder/process.rs b/drivers/android/binder/process.rs
index d09facebddf6..13ecd3048b89 100644
--- a/drivers/android/binder/process.rs
+++ b/drivers/android/binder/process.rs
@@ -901,7 +901,11 @@ pub(crate) fn insert_or_update_handle(
     pub(crate) fn get_transaction_node(&self, handle: u32) -> BinderResult<NodeRef> {
         // When handle is zero, try to get the context manager.
         if handle == 0 {
-            Ok(self.ctx.get_manager_node(true)?)
+            let node_ref = self.ctx.get_manager_node(true)?;
+            if self.task == node_ref.node.owner.task {
+                return Err(EINVAL.into());
+            }
+            Ok(node_ref)
         } else {
             Ok(self.get_node_from_handle(handle, true)?)
         }
-- 
2.39.5