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, 8 insertions, 3 deletions

diff --git a/libs/binder/Stability.cpp b/libs/binder/Stability.cpp
index 0a10a1d354..b6f10c8759 100644
--- a/libs/binder/Stability.cpp
+++ b/libs/binder/Stability.cpp
@@ -32,6 +32,11 @@ void Stability::debugLogStability(const std::string& tag, const sp<IBinder>& bin
     ALOGE("%s: stability is %s", tag.c_str(), stabilityString(get(binder.get())).c_str());
 }
 
+void Stability::markVndk(IBinder* binder) {
+    status_t result = set(binder, Level::VENDOR, true /*log*/);
+    LOG_ALWAYS_FATAL_IF(result != OK, "Should only mark known object.");
+}
+
 void Stability::tryMarkCompilationUnit(IBinder* binder) {
     (void) set(binder, kLocalStability, false /*log*/);
 }
@@ -95,9 +100,9 @@ bool Stability::check(int32_t provided, Level required) {
     }
 
     if (!stable) {
-        ALOGE("Interface with %s cannot accept interface with %s.",
-            stabilityString(required).c_str(),
-            stabilityString(provided).c_str());
+        ALOGE("Cannot do a user transaction on a %s binder in a %s context.",
+            stabilityString(provided).c_str(),
+            stabilityString(required).c_str());
     }
 
     return stable;