commit ea9d9d2caa6ce203022fe97d8ca789cb11fc88f4
author Alice Ryhl <aliceryhl@google.com> Fri Aug 27 07:51:30 2021 +0000
committer Alice Ryhl <aliceryhl@google.com> Wed Sep 15 13:02:52 2021 +0000
tree 9cbc4324ec68ad634faf9fd3f6797ddb0d8cbea1
parent 79abc0518eab5d832b1088faea291b48d921f1c7

ndk: Add way to manage ownership of linkToDeath cookie

Bug: 181971563
Bug: 197721058
Test: m, modified existing test
Change-Id: Ib9b4ab41fd7929f9ba56e112c8a5b58966040771

libs/binder/ndk/ibinder.cpp

diff --git a/libs/binder/ndk/ibinder.cpp b/libs/binder/ndk/ibinder.cpp
index 23db59e..83bf9be 100644
--- a/libs/binder/ndk/ibinder.cpp
+++ b/libs/binder/ndk/ibinder.cpp
@@ -373,6 +373,12 @@
     return clazz->getInterfaceDescriptorUtf8();
 }
 
+AIBinder_DeathRecipient::TransferDeathRecipient::~TransferDeathRecipient() {
+    if (mOnUnlinked != nullptr) {
+        mOnUnlinked(mCookie);
+    }
+}
+
 void AIBinder_DeathRecipient::TransferDeathRecipient::binderDied(const wp<IBinder>& who) {
     CHECK(who == mWho) << who.unsafe_get() << "(" << who.get_refs() << ") vs " << mWho.unsafe_get()
                        << " (" << mWho.get_refs() << ")";
@@ -394,7 +400,7 @@
 }
 
 AIBinder_DeathRecipient::AIBinder_DeathRecipient(AIBinder_DeathRecipient_onBinderDied onDied)
-    : mOnDied(onDied) {
+    : mOnDied(onDied), mOnUnlinked(nullptr) {
     CHECK(onDied != nullptr);
 }
 
@@ -412,10 +418,12 @@
     std::lock_guard<std::mutex> l(mDeathRecipientsMutex);
 
     sp<TransferDeathRecipient> recipient =
-            new TransferDeathRecipient(binder, cookie, this, mOnDied);
+            new TransferDeathRecipient(binder, cookie, this, mOnDied, mOnUnlinked);
 
     status_t status = binder->linkToDeath(recipient, cookie, 0 /*flags*/);
     if (status != STATUS_OK) {
+        // When we failed to link, the destructor of TransferDeathRecipient runs here, which
+        // ensures that mOnUnlinked is called before we return with an error from this method.
         return PruneStatusT(status);
     }
 
@@ -448,6 +456,10 @@
     return STATUS_NAME_NOT_FOUND;
 }
 
+void AIBinder_DeathRecipient::setOnUnlinked(AIBinder_DeathRecipient_onBinderUnlinked onUnlinked) {
+    mOnUnlinked = onUnlinked;
+}
+
 // start of C-API methods
 
 AIBinder* AIBinder_new(const AIBinder_Class* clazz, void* args) {
@@ -689,6 +701,15 @@
     return ret;
 }
 
+void AIBinder_DeathRecipient_setOnUnlinked(AIBinder_DeathRecipient* recipient,
+                                           AIBinder_DeathRecipient_onBinderUnlinked onUnlinked) {
+    if (recipient == nullptr) {
+        return;
+    }
+
+    recipient->setOnUnlinked(onUnlinked);
+}
+
 void AIBinder_DeathRecipient_delete(AIBinder_DeathRecipient* recipient) {
     if (recipient == nullptr) {
         return;