[Android] Fix Microdump generation when Seccomp-BPF is enabled.

content/common/sandbox_linux/android/sandbox_bpf_base_policy_android.cc

 // Copyright 2014 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 "content/common/sandbox_linux/android/sandbox_bpf_base_policy_android.h"
 
 #include <sys/syscall.h>
 #include <sys/types.h>
 
 #include "build/build_config.h"
@@ skipping 12 matching lines @@
 ResultExpr SandboxBPFBasePolicyAndroid::EvaluateSyscall(int sysno) const {
   bool override_and_allow = false;
 
   switch (sysno) {
     // TODO(rsesek): restrict clone parameters.
     case __NR_clone:
     case __NR_epoll_pwait:
     case __NR_flock:
 #if defined(__x86_64__) || defined(__aarch64__)
     case __NR_newfstatat:
+    case __NR_getdents64:
 #elif defined(__i386__) || defined(__arm__) || defined(__mips__)
     case __NR_fstatat64:
+    case __NR_getdents:
 #endif
     case __NR_getpriority:
     case __NR_ioctl:
     case __NR_mremap:
     // File system access cannot be restricted with seccomp-bpf on Android,
     // since the JVM classloader and other Framework features require file
     // access. It may be possible to restrict the filesystem with SELinux.
     // Currently we rely on the app/service UID isolation to create a
     // filesystem "sandbox".
 #if !defined(ARCH_CPU_ARM64)
     case __NR_open:
 #endif
     case __NR_openat:
     case __NR_pread64:
     case __NR_rt_sigtimedwait:
     case __NR_setpriority:
     case __NR_set_tid_address:
     case __NR_sigaltstack:
 #if defined(__i386__) || defined(__arm__)
     case __NR_ugetrlimit:
 #else
     case __NR_getrlimit:
 #endif
     case __NR_uname:
+
+    // Permit socket operations so that renderers can connect to logd and
+    // debuggerd.
+    case __NR_socket:

[mdempsky, 2016/02/05 18:31:46]

These seem scary.  Is there anything in place to prevent renderers from making
other arbitrary socket/connect calls?  Can we at least restrict socket() to only
create domain==AF_LOCAL/AF_UNIX sockets?

[Robert Sesek, 2016/02/05 19:57:12]

Yeah, I wasn't wild about having to add these, but it's necessary on Android. I
restricted it to PF_LOCAL/PF_UNIX and SOCK_DGRAM/SOCK_STREAM for now. SELinux
also provides some defense-in-depth here against opening network sockets from
isolated_app.

+    case __NR_connect:
+
+    // Ptrace is allowed so the Breakpad Microdumper can fork in a renderer
+    // and then ptrace the parent.
+    case __NR_ptrace:
       override_and_allow = true;
       break;
   }
 
   if (override_and_allow)
     return Allow();
 
   return SandboxBPFBasePolicy::EvaluateSyscall(sysno);
 }
 
 }  // namespace content