Add a check for the linux pkexec module

modules/exploits/linux/local/pkexec.rb

@@ -66,6 +66,20 @@ class MetasploitModule < Msf::Exploit::Local
     @executable_path
   end
 
+	def check
+		version = cmd_exec('pkexec --version')
+		if version.nil?
+			print_error "Policykit is not installed"
+			return CheckCode::Safe
+		end
+
+		if version.split('.')[1].to_f <= 0.101
+			return CheckCode::Vulnerable
+		end
+
+		CheckCode::Unknown
+	end
+
   def exploit
     main = %q^
 /*