libbinder: update getCallingPid docs

Bug: 297833427
Test: N/A
Change-Id: I406d2dbe68e79fa642df86f979a3f2332a4014bb
diff --git a/libs/binder/include/binder/IPCThreadState.h b/libs/binder/include/binder/IPCThreadState.h
index 9347ce4..dc5b1a1 100644
--- a/libs/binder/include/binder/IPCThreadState.h
+++ b/libs/binder/include/binder/IPCThreadState.h
@@ -62,8 +62,13 @@
 
             /**
              * Returns the PID of the process which has made the current binder
-             * call. If not in a binder call, this will return getpid. If the
-             * call is oneway, this will return 0.
+             * call. If not in a binder call, this will return getpid.
+             *
+             * Warning: oneway transactions do not receive PID. Even if you expect
+             * a transaction to be synchronous, a misbehaving client could send it
+             * as an asynchronous call and result in a 0 PID here. Additionally, if
+             * there is a race and the calling process dies, the PID may still be
+             * 0 for a synchronous call.
              */
             [[nodiscard]] pid_t getCallingPid() const;
 
diff --git a/libs/binder/ndk/include_ndk/android/binder_ibinder.h b/libs/binder/ndk/include_ndk/android/binder_ibinder.h
index db2d2c1..b1ab7b0 100644
--- a/libs/binder/ndk/include_ndk/android/binder_ibinder.h
+++ b/libs/binder/ndk/include_ndk/android/binder_ibinder.h
@@ -390,6 +390,12 @@
  * calling process dies and is replaced with another process with elevated permissions and the same
  * PID.
  *
+ * Warning: oneway transactions do not receive PID. Even if you expect
+ * a transaction to be synchronous, a misbehaving client could send it
+ * as a synchronous call and result in a 0 PID here. Additionally, if
+ * there is a race and the calling process dies, the PID may still be
+ * 0 for a synchronous call.
+ *
  * Available since API level 29.
  *
  * \return calling pid or the current process's PID if this thread isn't processing a transaction.
diff --git a/libs/binder/rust/src/state.rs b/libs/binder/rust/src/state.rs
index a3a2562..8a06274 100644
--- a/libs/binder/rust/src/state.rs
+++ b/libs/binder/rust/src/state.rs
@@ -101,13 +101,16 @@
     /// dies and is replaced with another process with elevated permissions and
     /// the same PID.
     ///
+    /// Warning: oneway transactions do not receive PID. Even if you expect
+    /// a transaction to be synchronous, a misbehaving client could send it
+    /// as a synchronous call and result in a 0 PID here. Additionally, if
+    /// there is a race and the calling process dies, the PID may still be
+    /// 0 for a synchronous call.
+    ///
     /// Available since API level 29.
     ///
     /// \return calling pid or the current process's PID if this thread isn't
     /// processing a transaction.
-    ///
-    /// If the transaction being processed is a oneway transaction, then this
-    /// method will return 0.
     pub fn get_calling_pid() -> pid_t {
         // Safety: Safe FFI
         unsafe { sys::AIBinder_getCallingPid() }