MQDescriptor: allow copies.

When scatter-gather is used in order to read an FMQ object from a
binder buffer, we are left with a 'const MQDescriptor<...>*' which
points into the binder buffer. When this descriptor is part of a struct
which is returned, and this struct is returned using a copy (not
scatter gather since the struct contains a non-fixed-width item like
an interface), it must be copied into the default constructed member of
that struct.

Change-Id: Iafb3ecafc2822e90662d49e1d3d53b12ffde650b
Fixes: 117239572
Test: hidl_test

1 files changed, 15 insertions, 8 deletions

diff --git a/base/include/hidl/MQDescriptor.h b/base/include/hidl/MQDescriptor.h
index 23be971..a8a176b 100644
--- a/base/include/hidl/MQDescriptor.h
+++ b/base/include/hidl/MQDescriptor.h
@@ -69,8 +69,8 @@ struct MQDescriptor {
     MQDescriptor();
     ~MQDescriptor();
 
-    explicit MQDescriptor(const MQDescriptor &other);
-    MQDescriptor &operator=(const MQDescriptor &other) = delete;
+    explicit MQDescriptor(const MQDescriptor& other) : MQDescriptor() { *this = other; }
+    MQDescriptor& operator=(const MQDescriptor& other);
 
     size_t getSize() const;
 
@@ -213,12 +213,17 @@ MQDescriptor<T, flavor>::MQDescriptor(size_t bufferSize, native_handle_t *nHandl
     }
 }
 
-template<typename T, MQFlavor flavor>
-MQDescriptor<T, flavor>::MQDescriptor(const MQDescriptor<T, flavor> &other)
-    : mGrantors(other.mGrantors),
-      mHandle(nullptr),
-      mQuantum(other.mQuantum),
-      mFlags(other.mFlags) {
+template <typename T, MQFlavor flavor>
+MQDescriptor<T, flavor>& MQDescriptor<T, flavor>::operator=(const MQDescriptor& other) {
+    mGrantors = other.mGrantors;
+    if (mHandle != nullptr) {
+        native_handle_close(mHandle);
+        native_handle_delete(mHandle);
+        mHandle = nullptr;
+    }
+    mQuantum = other.mQuantum;
+    mFlags = other.mFlags;
+
     if (other.mHandle != nullptr) {
         mHandle = native_handle_create(
                 other.mHandle->numFds, other.mHandle->numInts);
@@ -231,6 +236,8 @@ MQDescriptor<T, flavor>::MQDescriptor(const MQDescriptor<T, flavor> &other)
                &other.mHandle->data[other.mHandle->numFds],
                other.mHandle->numInts * sizeof(int));
     }
+
+    return *this;
 }
 
 template<typename T, MQFlavor flavor>