libbinder_rs: Handle empty args list for dump transactions

Previously we expected the args pointer passed to the handler for dump
transactions to be non-null. If there are no arguments this
pointer may be null and we should pass an empty args list instead of
erroring out.

Bug: 232887857
Test: atest -p frameworks/native/libs/binder
Test: cts -m  CtsSecurityTestCases -t android.security.cts.ServicePermissionsTest#testDumpProtected
Change-Id: If2b08c688a374913ef0913749efc72db07e7776f

1 files changed, 8 insertions, 3 deletions

diff --git a/libs/binder/rust/src/native.rs b/libs/binder/rust/src/native.rs
index b7c7ae4b54..3edeebf892 100644
--- a/libs/binder/rust/src/native.rs
+++ b/libs/binder/rust/src/native.rs
@@ -335,11 +335,16 @@ impl<T: Remotable> InterfaceClassMethods for Binder<T> {
         // We don't own this file, so we need to be careful not to drop it.
         let file = ManuallyDrop::new(File::from_raw_fd(fd));
 
-        if args.is_null() {
+        if args.is_null() && num_args != 0 {
             return StatusCode::UNEXPECTED_NULL as status_t;
         }
-        let args = slice::from_raw_parts(args, num_args as usize);
-        let args: Vec<_> = args.iter().map(|s| CStr::from_ptr(*s)).collect();
+
+        let args = if args.is_null() || num_args == 0 {
+            vec![]
+        } else {
+            slice::from_raw_parts(args, num_args as usize)
+                .iter().map(|s| CStr::from_ptr(*s)).collect()
+        };
 
         let object = sys::AIBinder_getUserData(binder);
         let binder: &T = &*(object as *const T);