Start all children in their own PID namespace.

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 2e66d97cf53a45895d0ea7caeb1e8315f0a510a8..4a606db6432175aa90f2c40169b43f7e05345ece 100644
--- a/sandbox/linux/services/credentials.cc
+++ b/sandbox/linux/services/credentials.cc
@@ -125,6 +125,7 @@ int LinuxCapabilityToKernelValue(LinuxCapability cap) {
 
 }  // namespace.
 
+// static
 bool Credentials::DropAllCapabilities(int proc_fd) {
   if (!SetCapabilities(proc_fd, std::vector<LinuxCapability>())) {
     return false;
@@ -134,22 +135,20 @@ bool Credentials::DropAllCapabilities(int proc_fd) {
   return true;
 }
 
+// static
 bool Credentials::DropAllCapabilities() {
   base::ScopedFD proc_fd(ProcUtil::OpenProc());
   return Credentials::DropAllCapabilities(proc_fd.get());
 }
 
 // static
-bool Credentials::SetCapabilities(int proc_fd,
-                                  const std::vector<LinuxCapability>& caps) {
-  DCHECK_LE(0, proc_fd);
-
-#if !defined(THREAD_SANITIZER)
-  // With TSAN, accept to break the security model as it is a testing
-  // configuration.
-  CHECK(ThreadHelpers::IsSingleThreaded(proc_fd));
-#endif
+bool Credentials::DropAllCapabilitiesOnCurrentThread() {
+  return SetCapabilitiesOnCurrentThread(std::vector<LinuxCapability>());
+}
 
+// static
+bool Credentials::SetCapabilitiesOnCurrentThread(
+    const std::vector<LinuxCapability>& caps) {
   struct cap_hdr hdr = {};
   hdr.version = _LINUX_CAPABILITY_VERSION_3;
   struct cap_data data[_LINUX_CAPABILITY_U32S_3] = {{}};
@@ -167,6 +166,20 @@ bool Credentials::SetCapabilities(int proc_fd,
   return sys_capset(&hdr, data) == 0;
 }
 
+// static
+bool Credentials::SetCapabilities(int proc_fd,
+                                  const std::vector<LinuxCapability>& caps) {
+  DCHECK_LE(0, proc_fd);
+
+#if !defined(THREAD_SANITIZER)
+  // With TSAN, accept to break the security model as it is a testing
+  // configuration.
+  CHECK(ThreadHelpers::IsSingleThreaded(proc_fd));
+#endif
+
+  return SetCapabilitiesOnCurrentThread(caps);
+}
+
 bool Credentials::HasAnyCapability() {
   struct cap_hdr hdr = {};
   hdr.version = _LINUX_CAPABILITY_VERSION_3;