sandbox: use waitpid consistently

sandbox/linux/services/credentials.cc

Index: sandbox/linux/services/credentials.cc
diff --git a/sandbox/linux/services/credentials.cc b/sandbox/linux/services/credentials.cc
index e571ddec59776a58a1810b22bf83ba4c63b8ba58..3762106aa18c2b7ab3089d75f6068c19658b9712 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -114,7 +114,7 @@ bool ChrootToSafeEmptyDir() {
   int status = -1;
   PCHECK(HANDLE_EINTR(waitpid(pid, &status, 0)) == pid);
 
-  return kExitSuccess == status;
+  return WIFEXITED(status) && WEXITSTATUS(status) == kExitSuccess;

[jln (very slow on Chromium), 2015/02/19 03:59:59]

ugh, thanks :/

 }
 
 // CHECK() that an attempt to move to a new user namespace raised an expected
@@ -178,8 +178,10 @@ bool Credentials::CanCreateProcessInNewUserNS() {
   }
 
   // Always reap the child.
-  siginfo_t infop;
-  PCHECK(0 == HANDLE_EINTR(waitid(P_PID, pid, &infop, WEXITED)));
+  int status = -1;
+  PCHECK(HANDLE_EINTR(waitpid(pid, &status, 0)) == pid);
+  CHECK(WIFEXITED(status));
+  CHECK_EQ(0, WEXITSTATUS(status));

[jln (very slow on Chromium), 2015/02/19 03:59:59]

Since you're now checking the exit code, do you want to use kExitSuccess here
and in _exit() above?

[mdempsky, 2015/02/19 04:02:51]

Done.

 
   // clone(2) succeeded, we can use CLONE_NEWUSER.
   return true;