Update from https://crrev.com/317530

sandbox/linux/services/credentials.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "sandbox/linux/services/credentials.h"
 
 #include <errno.h>
 #include <signal.h>
 #include <stdio.h>
 #include <sys/capability.h>
@@ skipping 96 matching lines @@
 #error "Unsupported architecture"
 #endif
   pid = clone(ChrootToSelfFdinfo, stack,
               CLONE_VM | CLONE_VFORK | CLONE_FS | SIGCHLD, nullptr, nullptr,
               nullptr, nullptr);
   PCHECK(pid != -1);
 
   int status = -1;
   PCHECK(HANDLE_EINTR(waitpid(pid, &status, 0)) == pid);
 
-  return kExitSuccess == status;
+  return WIFEXITED(status) && WEXITSTATUS(status) == kExitSuccess;
 }
 
 // CHECK() that an attempt to move to a new user namespace raised an expected
 // errno.
 void CheckCloneNewUserErrno(int error) {
   // EPERM can happen if already in a chroot. EUSERS if too many nested
   // namespaces are used. EINVAL for kernels that don't support the feature.
   // Valgrind will ENOSYS unshare().
   PCHECK(error == EPERM || error == EUSERS || error == EINVAL ||
          error == ENOSYS);
@@ skipping 39 matching lines @@
 
   if (pid == -1) {
     CheckCloneNewUserErrno(errno);
     return false;
   }
 
   // The parent process could have had threads. In the child, these threads
   // have disappeared. Make sure to not do anything in the child, as this is a
   // fragile execution environment.
   if (pid == 0) {
-    _exit(0);
+    _exit(kExitSuccess);
   }
 
   // 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(kExitSuccess, WEXITSTATUS(status));
 
   // clone(2) succeeded, we can use CLONE_NEWUSER.
   return true;
 }
 
 bool Credentials::MoveToNewUserNS() {
   uid_t uid;
   gid_t gid;
   if (!GetRESIds(&uid, &gid)) {
     // If all the uids (or gids) are not equal to each other, the security
@@ skipping 26 matching lines @@
 }
 
 bool Credentials::DropFileSystemAccess() {
   CHECK(ChrootToSafeEmptyDir());
   CHECK(!base::DirectoryExists(base::FilePath("/proc")));
   // We never let this function fail.
   return true;
 }
 
 }  // namespace sandbox.