Merge 161443 - Seccomp BPF: handle EINTR in error reporting setup.

sandbox/linux/seccomp-bpf/sandbox_bpf.cc

 // Copyright (c) 2012 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 <time.h>
 
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #include "sandbox/linux/seccomp-bpf/verifier.h"
 
 // The kernel gives us a sandbox, we turn it into a playground :-)
@@ skipping 66 matching lines @@
     // into running without a sandbox.
     sigprocmask(SIG_SETMASK, &oldMask, NULL);  // OK, if it fails
     SANDBOX_DIE("fork() failed unexpectedly");
   }
 
   // In the child process
   if (!pid) {
     // Test a very simple sandbox policy to verify that we can
     // successfully turn on sandboxing.
     Die::EnableSimpleExit();
+    errno = 0;
     if (HANDLE_EINTR(close(fds[0])) ||
-        dup2(fds[1], 2) != 2 ||
+        HANDLE_EINTR(dup2(fds[1], 2)) != 2 ||
         HANDLE_EINTR(close(fds[1]))) {
-      static const char msg[] = "Failed to set up stderr\n";
-      if (HANDLE_EINTR(write(fds[1], msg, sizeof(msg)-1))) { }
+      const char* error_string = strerror(errno);
+      static const char msg[] = "Failed to set up stderr: ";
+      if (HANDLE_EINTR(write(fds[1], msg, sizeof(msg)-1)) > 0 && error_string &&
+          HANDLE_EINTR(write(fds[1], error_string, strlen(error_string))) > 0 &&
+          HANDLE_EINTR(write(fds[1], "\n", 1))) {
+      }
     } else {
       evaluators_.clear();
       setSandboxPolicy(syscallEvaluator, NULL);
       setProcFd(proc_fd);
 
       // By passing "quiet=true" to "startSandboxInternal()" we suppress
       // messages for expected and benign failures (e.g. if the current
       // kernel lacks support for BPF filters).
       startSandboxInternal(true);
 
@@ skipping 614 matching lines @@
 Sandbox::SandboxStatus Sandbox::status_ = STATUS_UNKNOWN;
 int    Sandbox::proc_fd_                = -1;
 Sandbox::Evaluators Sandbox::evaluators_;
 Sandbox::ErrMap Sandbox::errMap_;
 Sandbox::Traps *Sandbox::traps_         = NULL;
 Sandbox::TrapIds Sandbox::trapIds_;
 ErrorCode *Sandbox::trapArray_          = NULL;
 size_t Sandbox::trapArraySize_          = 0;
 
 }  // namespace