sandbox-bpf: more robust probe process in release mode

sandbox/linux/seccomp-bpf/sandbox_bpf.cc

Index: sandbox/linux/seccomp-bpf/sandbox_bpf.cc
diff --git a/sandbox/linux/seccomp-bpf/sandbox_bpf.cc b/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
index ff855b8a9cb131119963fd0829544b5f00e41b2b..0f144ce89c1b24d43b26ecb78a041dd7459686fc 100644
--- a/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
+++ b/sandbox/linux/seccomp-bpf/sandbox_bpf.cc
@@ -20,6 +20,11 @@
 #error Big endian operation is untested and expected to be broken
 #endif
 
+#ifndef SECCOMP_BPF_STANDALONE
+#include "base/logging.h"
+#include "base/posix/eintr_wrapper.h"
+#endif
+
 #include "sandbox/linux/seccomp-bpf/codegen.h"
 #include "sandbox/linux/seccomp-bpf/sandbox_bpf.h"
 #include "sandbox/linux/seccomp-bpf/syscall.h"
@@ -30,7 +35,9 @@ namespace {
 
 void WriteFailedStderrSetupMessage(int out_fd) {
   const char* error_string = strerror(errno);
-  static const char msg[] = "Failed to set up stderr: ";
+  static const char msg[] = "You have reproduced a puzzling issue.\n"
+                            "Please, report to crbug.com/152530!\n"
+                            "Failed to set up stderr: ";
   if (HANDLE_EINTR(write(out_fd, msg, sizeof(msg)-1)) > 0 && error_string &&
       HANDLE_EINTR(write(out_fd, error_string, strlen(error_string))) > 0 &&
       HANDLE_EINTR(write(out_fd, "\n", 1))) {
@@ -151,9 +158,14 @@ bool Sandbox::RunFunctionInPolicy(void (*CodeInSandbox)(),
     // successfully turn on sandboxing.
     Die::EnableSimpleExit();
 
+    errno = 0;
     if (HANDLE_EINTR(close(fds[0]))) {
+      // This call to close() has been failing in strange ways. See
+      // crbug.com/152530. So we only fail in debug mode now.
+#if !defined(NDEBUG)
       WriteFailedStderrSetupMessage(fds[1]);
       SANDBOX_DIE(NULL);
+#endif
     }
     if (HANDLE_EINTR(dup2(fds[1], 2)) != 2) {
       // Stderr could very well be a file descriptor to .xsession-errors, or
@@ -163,10 +175,19 @@ bool Sandbox::RunFunctionInPolicy(void (*CodeInSandbox)(),
       // If dup2 fails here, we will continue normally, this means that our
       // parent won't cause a fatal failure if something writes to stderr in
       // this child.
+#if !defined(NDEBUG)
+      // In DEBUG builds, we still want to get a report.
+      WriteFailedStderrSetupMessage(fds[1]);
+      SANDBOX_DIE(NULL);
+#endif
     }
     if (HANDLE_EINTR(close(fds[1]))) {
+      // This call to close() has been failing in strange ways. See
+      // crbug.com/152530. So we only fail in debug mode now.
+#if !defined(NDEBUG)
       WriteFailedStderrSetupMessage(fds[1]);
       SANDBOX_DIE(NULL);
+#endif
     }
 
     evaluators_.clear();