debuggerd_handler: use syscall(__NR_get[pt]id) instead of get[pt]id.

bionic's cached values for getpid/gettid can be invalid if the crashing
process manually invoked clone to create a thread or process, which
will lead the crash_dump refusing to do anything, because it sees the
actual values.

Use the getpid/gettid syscalls directly to ensure correct values on
this end.

Bug: http://b/37769298
Test: debuggerd_test
Change-Id: I0b1e652beb1a66e564a48b88ed7fa971d61c6ff9

1 files changed, 35 insertions, 3 deletions

diff --git a/debuggerd/debuggerd_test.cpp b/debuggerd/debuggerd_test.cpp
index 568879ed5..0b4bbfb60 100644
--- a/debuggerd/debuggerd_test.cpp
+++ b/debuggerd/debuggerd_test.cpp
@@ -29,6 +29,7 @@
 
 #include <android-base/file.h>
 #include <android-base/logging.h>
+#include <android-base/macros.h>
 #include <android-base/parseint.h>
 #include <android-base/properties.h>
 #include <android-base/strings.h>
@@ -149,7 +150,7 @@ class CrasherTest : public ::testing::Test {
   // Returns -1 if we fail to read a response from tombstoned, otherwise the received return code.
   void FinishIntercept(int* result);
 
-  void StartProcess(std::function<void()> function);
+  void StartProcess(std::function<void()> function, std::function<pid_t()> forker = fork);
   void StartCrasher(const std::string& crash_type);
   void FinishCrasher();
   void AssertDeath(int signo);
@@ -195,14 +196,14 @@ void CrasherTest::FinishIntercept(int* result) {
   }
 }
 
-void CrasherTest::StartProcess(std::function<void()> function) {
+void CrasherTest::StartProcess(std::function<void()> function, std::function<pid_t()> forker) {
   unique_fd read_pipe;
   unique_fd crasher_read_pipe;
   if (!Pipe(&crasher_read_pipe, &crasher_pipe)) {
     FAIL() << "failed to create pipe: " << strerror(errno);
   }
 
-  crasher_pid = fork();
+  crasher_pid = forker();
   if (crasher_pid == -1) {
     FAIL() << "fork failed: " << strerror(errno);
   } else if (crasher_pid == 0) {
@@ -527,6 +528,37 @@ TEST_F(CrasherTest, capabilities) {
   ASSERT_MATCH(result, R"(#00 pc [0-9a-f]+\s+ /system/lib)" ARCH_SUFFIX R"(/libc.so \(tgkill)");
 }
 
+TEST_F(CrasherTest, fake_pid) {
+  int intercept_result;
+  unique_fd output_fd;
+
+  // Prime the getpid/gettid caches.
+  UNUSED(getpid());
+  UNUSED(gettid());
+
+  std::function<pid_t()> clone_fn = []() {
+    return syscall(__NR_clone, SIGCHLD, nullptr, nullptr, nullptr, nullptr);
+  };
+  StartProcess(
+      []() {
+        ASSERT_NE(getpid(), syscall(__NR_getpid));
+        ASSERT_NE(gettid(), syscall(__NR_gettid));
+        raise(SIGSEGV);
+      },
+      clone_fn);
+
+  StartIntercept(&output_fd);
+  FinishCrasher();
+  AssertDeath(SIGSEGV);
+  FinishIntercept(&intercept_result);
+
+  ASSERT_EQ(1, intercept_result) << "tombstoned reported failure";
+
+  std::string result;
+  ConsumeFd(std::move(output_fd), &result);
+  ASSERT_MATCH(result, R"(#00 pc [0-9a-f]+\s+ /system/lib)" ARCH_SUFFIX R"(/libc.so \(tgkill)");
+}
+
 TEST(crash_dump, zombie) {
   pid_t forkpid = fork();