Merge pull request #7806 from rubygems/deivid-rodriguez/safe-windows-binstubs

Protect creating binstubs with a file lock

(cherry picked from commit ebb535e)

Author: deivid-rodriguez

lib/rubygems.rb

@@ -760,6 +760,7 @@ def self.read_binary(path)
 
   ##
   # Safely write a file in binary mode on all platforms.
+
   def self.write_binary(path, data)
     open_file(path, "wb") do |io|
       io.write data
@@ -771,33 +772,30 @@ def self.write_binary(path, data)
   end
 
   ##
-  # Open a file with given flags. It requires special logic on Windows, like
-  # protecting access with flock
+  # Open a file with given flags
 
   def self.open_file(path, flags, &block)
-    if !java_platform? && win_platform?
-      open_file_with_flock(path, flags, &block)
-    else
-      open_file_without_flock(path, flags, &block)
-    end
+    File.open(path, flags, &block)
   end
 
   ##
   # Open a file with given flags, and protect access with flock
 
-  def self.open_file_with_flock(path, flags, &block)
+  def self.open_file_with_flock(path, &block)
+    flags = File.exist?(path) ? "r+" : "a+"
+
     File.open(path, flags) do |io|
       begin
         io.flock(File::LOCK_EX)
       rescue Errno::ENOSYS, Errno::ENOTSUP
       end
       yield io
-    end
-  rescue Errno::ENOLCK # NFS
-    if Thread.main != Thread.current
-      raise
-    else
-      open_file_without_flock(path, flags, &block)
+    rescue Errno::ENOLCK # NFS
+      if Thread.main != Thread.current
+        raise
+      else
+        open_file(path, flags, &block)
+      end
     end
   end
 
@@ -1297,10 +1295,6 @@ def clear_default_specs
 
     private
 
-    def open_file_without_flock(path, flags, &block)
-      File.open(path, flags, &block)
-    end
-
     def already_loaded?(file)
       $LOADED_FEATURES.any? do |feature_path|
         feature_path.end_with?(file) && default_gem_load_paths.any? {|load_path_entry| feature_path == "#{load_path_entry}/#{file}" }

lib/rubygems/installer.rb

@@ -222,7 +222,7 @@ def check_executable_overwrite(filename) # :nodoc:
     ruby_executable = false
     existing = nil
 
-    Gem.open_file_with_flock generated_bin, "rb+" do |io|
+    File.open generated_bin, "rb" do |io|
       line = io.gets
       shebang = /^#!.*ruby/o
 
@@ -500,8 +500,7 @@ def generate_bin # :nodoc:
       dir_mode = options[:prog_mode] || (mode | 0o111)
 
       unless dir_mode == mode
-        require "fileutils"
-        FileUtils.chmod dir_mode, bin_path
+        File.chmod dir_mode, bin_path
       end
 
       check_executable_overwrite filename
@@ -539,12 +538,14 @@ def generate_plugins # :nodoc:
   def generate_bin_script(filename, bindir)
     bin_script_path = File.join bindir, formatted_program_filename(filename)
 
-    require "fileutils"
-    FileUtils.rm_f bin_script_path # prior install may have been --no-wrappers
+    Gem.open_file_with_flock("#{bin_script_path}.lock") do
+      require "fileutils"
+      FileUtils.rm_f bin_script_path # prior install may have been --no-wrappers
 
-    File.open bin_script_path, "wb", 0o755 do |file|
-      file.print app_script_text(filename)
-      file.chmod(options[:prog_mode] || 0o755)
+      File.open(bin_script_path, "wb", 0o755) do |file|
+        file.write app_script_text(filename)
+        file.chmod(options[:prog_mode] || 0o755)
+      end
     end
 
     verbose bin_script_path