Kernel: Reset the process dumpable flag on successful non-setid exec

Once we've committed to a new memory layout and non-setid credentials,
we can reset the dumpable flag.

Kernel/Syscalls/execve.cpp

@@ -363,23 +363,23 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
  auto old_suid = m_suid;
  auto old_egid = m_egid;
  auto old_sgid = m_sgid;
- auto was_dumpable = is_dumpable();
 
  ArmedScopeGuard cred_restore_guard = [&] {
  m_euid = old_euid;
  m_suid = old_suid;
  m_egid = old_egid;
  m_sgid = old_sgid;
- set_dumpable(was_dumpable);
  };
 
+ bool executable_is_setid = false;
+
  if (!(main_program_description->custody()->mount_flags() & MS_NOSUID)) {
  if (main_program_metadata.is_setuid()) {
- set_dumpable(false);
+ executable_is_setid = true;
  m_euid = m_suid = main_program_metadata.uid;
  }
  if (main_program_metadata.is_setgid()) {
- set_dumpable(false);
+ executable_is_setid = true;
  m_egid = m_sgid = main_program_metadata.gid;
  }
  }
@@ -417,6 +417,8 @@ int Process::do_exec(NonnullRefPtr<FileDescription> main_program_description, Ve
 
  disown_all_shared_buffers();
 
+ set_dumpable(!executable_is_setid);
+
  for (size_t i = 0; i < m_fds.size(); ++i) {
  auto& description_and_flags = m_fds[i];
  if (description_and_flags.description() && description_and_flags.flags() & FD_CLOEXEC)