Fix garbage detection within SSH communicator

Fixes #10552

plugins/communicators/ssh/communicator.rb

@@ -573,14 +573,14 @@ module VagrantPlugins
                 stderr_data_buffer << data
                 marker_index = stderr_data_buffer.index(CMD_GARBAGE_MARKER)
                 if marker_index
-                  marker_found = true
+                  stderr_marker_found = true
                   stderr_data_buffer.slice!(0, marker_index + CMD_GARBAGE_MARKER.size)
                   data.replace(stderr_data_buffer)
-                  data_buffer = nil
+                  stderr_data_buffer = nil
                 end
               end
 
-              if block_given? && marker_found && !data.empty?
+              if block_given? && stderr_marker_found && !data.empty?
                 yield :stderr, data
               end
             end

test/unit/plugins/communicators/ssh/communicator_test.rb

@@ -321,6 +321,7 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
       let(:command_stdout_data) do
         "Line of garbage\nMore garbage\n#{command_garbage_marker}bin\ntmp\n"
       end
+      let(:command_stderr_data) { "some data" }
 
       it "removes any garbage output prepended to command output" do
         stdout = ''
@@ -333,12 +334,23 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
         ).to eq(0)
         expect(stdout).to eq("bin\ntmp\n")
       end
+
+      it "should not receive any stderr data" do
+        stderr = ''
+        communicator.execute("ls /") do |type, data|
+          if type == :stderr
+            stderr << data
+          end
+        end
+        expect(stderr).to be_empty
+      end
     end
 
     context "with no command output" do
       let(:command_stdout_data) do
         "#{command_garbage_marker}"
       end
+      let(:command_stderr_data) { "some data" }
 
       it "does not send empty stdout data string" do
         empty = true
@@ -351,12 +363,23 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
         ).to eq(0)
         expect(empty).to be(true)
       end
+
+      it "should not receive any stderr data" do
+        stderr = ''
+        communicator.execute("ls /") do |type, data|
+          if type == :stderr
+            stderr << data
+          end
+        end
+        expect(stderr).to be_empty
+      end
     end
 
     context "with garbage content prepended to command stderr output" do
       let(:command_stderr_data) do
         "Line of garbage\nMore garbage\n#{command_garbage_marker}bin\ntmp\n"
       end
+      let(:command_stdout_data) { "some data" }
 
       it "removes any garbage output prepended to command stderr output" do
         stderr = ''
@@ -369,12 +392,23 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
         ).to eq(0)
         expect(stderr).to eq("bin\ntmp\n")
       end
+
+      it "should not receive any stdout data" do
+        stdout = ''
+        communicator.execute("ls /") do |type, data|
+          if type == :stdout
+            stdout << data
+          end
+        end
+        expect(stdout).to be_empty
+      end
     end
 
     context "with no command output on stderr" do
       let(:command_stderr_data) do
         "#{command_garbage_marker}"
       end
+      let(:command_std_data) { "some data" }
 
       it "does not send empty stderr data string" do
         empty = true
@@ -387,6 +421,16 @@ describe VagrantPlugins::CommunicatorSSH::Communicator do
         ).to eq(0)
         expect(empty).to be(true)
       end
+
+      it "should not receive any stdout data" do
+        stdout = ''
+        communicator.execute("ls /") do |type, data|
+          if type == :stdout
+            stdout << data
+          end
+        end
+        expect(stdout).to be_empty
+      end
     end
 
     context "with pty enabled" do