[rubygems/rubygems] Properly protect writing binstubs with a file lock
There's an issue when multiple processes try to write the same binstub. The problem is that our file locking mechanism is incorrect because files are truncated _before_ they are locked. So it can happen that: * Process A truncates binstub FOO. * Process B truncates binstub FOO. * Process A writes binstub FOO for gem BAR from the beginning of file. * Process B writes binstub FOO for gem BAZ from the beginning of file. If binstub FOO for gem BAR is bigger than binstub FOO for gem BAZ, then some bytes will be left around at the end of the binstub, making it corrupt. This was not a problem in our specs until the spec testing binstubs with the same name coming from different gems changed from using gems named "fake" and "rack" to using gems named "fake" and "myrack". Because of the difference in gem name length, the generated binstub for gem "myrack" is now longer, causing the above problem if binstub for gem myrack is written first. The solution is to make sure when using flock to always use modes that DON'T truncate the file when opening it. So, we use `r+` if the file exists previously (it requires the file to exist previously), otherwise we use `a+`. https://github.com/rubygems/rubygems/commit/ce8bcba90f
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@ -792,21 +792,18 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
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end
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##
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# Open a file with given flags. It requires special logic on Windows, like
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# protecting access with flock
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# Open a file with given flags
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def self.open_file(path, flags, &block)
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if !java_platform? && win_platform?
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open_file_with_flock(path, flags, &block)
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else
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open_file_without_flock(path, flags, &block)
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end
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File.open(path, flags, &block)
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end
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##
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# Open a file with given flags, and protect access with flock
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def self.open_file_with_flock(path, flags, &block)
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def self.open_file_with_flock(path, &block)
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flags = File.exist?(path) ? "r+" : "a+"
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File.open(path, flags) do |io|
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begin
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io.flock(File::LOCK_EX)
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@ -817,7 +814,7 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
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if Thread.main != Thread.current
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raise
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else
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open_file_without_flock(path, flags, &block)
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open_file(path, flags, &block)
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end
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end
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end
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@ -1318,10 +1315,6 @@ An Array (#{env.inspect}) was passed in from #{caller[3]}
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private
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def open_file_without_flock(path, flags, &block)
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File.open(path, flags, &block)
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end
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def already_loaded?(file)
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$LOADED_FEATURES.any? do |feature_path|
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feature_path.end_with?(file) && default_gem_load_paths.any? {|load_path_entry| feature_path == "#{load_path_entry}/#{file}" }
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@ -222,7 +222,7 @@ class Gem::Installer
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ruby_executable = false
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existing = nil
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Gem.open_file_with_flock generated_bin, "rb+" do |io|
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File.open generated_bin, "rb" do |io|
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line = io.gets
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shebang = /^#!.*ruby/o
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@ -541,8 +541,8 @@ class Gem::Installer
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require "fileutils"
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FileUtils.rm_f bin_script_path # prior install may have been --no-wrappers
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File.open bin_script_path, "wb", 0o755 do |file|
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file.print app_script_text(filename)
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Gem.open_file_with_flock(bin_script_path) do |file|
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file.write app_script_text(filename)
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file.chmod(options[:prog_mode] || 0o755)
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end
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