libbinder: stability check moved to trans time

Before: stability check done when binder is read from a parcel
After: stability check done when binder is transacted on

Why this change is being made/benefits:
- vendor binders can be used as tokens in system context
- pingBinder/interfaceChain/etc.. can be done on vendor binders in a
system context, so code can generically operate on binders. This is
particularly useful for service manager and dumpstate, which previously
I was going to special-case
- policy on which binders go where is entirely reliant on SELinux
whereas before there were additional runtime restrictions

Cons to this change:
- allowed binders must be determined by context. BpBinder now checks
stability based on kLocalStability. More work would need to be done to
get this working with APEX.

Bug: 136027762
Test: binderStabilityTest
Change-Id: Iff026e81a130dbb8885ca82ec24e69a5768847eb
Merged-In: Iff026e81a130dbb8885ca82ec24e69a5768847eb

1 files changed, 3 insertions, 12 deletions

diff --git a/libs/binder/Parcel.cpp b/libs/binder/Parcel.cpp
index a2333ae07e..c75f0365f5 100644
--- a/libs/binder/Parcel.cpp
+++ b/libs/binder/Parcel.cpp
@@ -35,6 +35,7 @@
 #include <binder/IPCThreadState.h>
 #include <binder/Parcel.h>
 #include <binder/ProcessState.h>
+#include <binder/Stability.h>
 #include <binder/Status.h>
 #include <binder/TextOutput.h>
 
@@ -167,11 +168,10 @@ static void release_object(const sp<ProcessState>& proc,
 status_t Parcel::finishFlattenBinder(
     const sp<IBinder>& /*binder*/, const flat_binder_object& flat)
 {
-    // internal::Stability::tryMarkCompilationUnit(binder.get());
-
     status_t status = writeObject(flat, false);
     if (status != OK) return status;
 
+    // internal::Stability::tryMarkCompilationUnit(binder.get());
     // Cannot change wire protocol w/o SM update
     // return writeInt32(internal::Stability::get(binder.get()));
     return OK;
@@ -185,10 +185,6 @@ status_t Parcel::finishUnflattenBinder(
     // status_t status = readInt32(&stability);
     // if (status != OK) return status;
 
-    // if (binder != nullptr && !internal::Stability::check(stability, mRequiredStability)) {
-    //     return BAD_TYPE;
-    // }
-
     // status = internal::Stability::set(binder.get(), stability, true /*log*/);
     // if (status != OK) return status;
 
@@ -356,10 +352,6 @@ status_t Parcel::setDataCapacity(size_t size)
     return NO_ERROR;
 }
 
-void Parcel::setTransactingBinder(const sp<IBinder>& binder) const {
-    mRequiredStability = internal::Stability::get(binder.get());
-}
-
 status_t Parcel::setData(const uint8_t* buffer, size_t len)
 {
     if (len > INT32_MAX) {
@@ -2615,10 +2607,9 @@ void Parcel::initState()
     mObjectsCapacity = 0;
     mNextObjectHint = 0;
     mObjectsSorted = false;
-    mAllowFds = true;
     mHasFds = false;
     mFdsKnown = true;
-    mRequiredStability = internal::Stability::UNDECLARED;
+    mAllowFds = true;
     mOwner = nullptr;
     mOpenAshmemSize = 0;