libbinder: added enforceNoDataAvail()

enforceNoDataAvail() verifies that there's no bytes left to be read on
the Parcel.

Bug: 208509444
Test: atest binderUnitTest
Test: binder_parcel_fuzzer
Change-Id: I469c8778fa54f3db27f00a9df8db668a0c4c76bc

1 files changed, 11 insertions, 0 deletions

diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index 7027a4b0a3..6fb189cd70 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -739,6 +739,17 @@ bool Parcel::enforceInterface(const char16_t* interface,
     }
 }
 
+binder::Status Parcel::enforceNoDataAvail() const {
+    const auto n = dataAvail();
+    if (n == 0) {
+        return binder::Status::ok();
+    }
+    return binder::Status::
+            fromExceptionCode(binder::Status::Exception::EX_BAD_PARCELABLE,
+                              String8::format("Parcel data not fully consumed, unread size: %zu",
+                                              n));
+}
+
 size_t Parcel::objectsCount() const
 {
     return mObjectsSize;