Check for leaking FDs in binder_parcel_fuzzer

Ignore-AOSP-First: na
Flag: TEST_ONLY
Test: binder_parcel_fuzzer
Bug: 406499223
Change-Id: I65aa5ebd753c58041feb77c5b2de8abc3ca677a5

Author: devinmoore-goog

libs/binder/tests/parcel_fuzzer/main.cpp

@@ -28,10 +28,11 @@
 #include <fuzzbinder/random_parcel.h>
 #include <fuzzer/FuzzedDataProvider.h>
 
-#include <cstdlib>
-#include <ctime>
 #include <sys/resource.h>
 #include <sys/time.h>
+#include <cstdlib>
+#include <ctime>
+#include <filesystem>
 
 #include "../../Utils.h"
 
@@ -157,12 +158,21 @@ static AIBinder_Class* kNothingClass =
         AIBinder_Class_define("nothing", NothingClass_onCreate, NothingClass_onDestroy,
                               NothingClass_onTransact);
 
+static long numFds() {
+    return std::distance(std::filesystem::directory_iterator("/proc/self/fd"),
+                         std::filesystem::directory_iterator{});
+}
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
     if (size <= 1) return 0;  // no use
 
     // avoid timeouts, see b/142617274, b/142473153
     if (size > 50000) return 0;
 
+    struct rlimit limit{};
+    CHECK_EQ(0, getrlimit(RLIMIT_NOFILE, &limit));
+    uint64_t maxFds = limit.rlim_cur;
+    int initialFds = numFds();
+
     FuzzedDataProvider provider = FuzzedDataProvider(data, size);
 
     const std::function<void(FuzzedDataProvider&&)> fuzzBackend[] = {
@@ -209,5 +219,6 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
 
     provider.PickValueInArray(fuzzBackend)(std::move(provider));
 
+    CHECK_EQ(initialFds, numFds()) << "FDs are being leaked";
     return 0;
 }