File.cp_r! regression when copy from read-only fs

[delitrem]

Elixir and Erlang/OTP versions

Erlang/OTP 27 [erts-15.2.7.4] [source] [64-bit] [smp:16:16] [ds:16:16:10] [async-threads:1] [jit:ns]

Elixir 1.20.0-rc.4 (9e4eb3d) (compiled with Erlang/OTP 27)

Operating system

Guix System (NixOS-like Linux distro)

Current behavior

Read-only directories can't be copied recursively because destination directories inherit permissions from the source directory without postpone.

How to reproduce:

% mkdir src-dir
% touch src-dir/test
% chmod -w -R src-dir
% ~/src/elixir/elixir/bin/iex
iex(1)> File.cp_r!("src-dir", "dst-dir")
** (File.CopyError) could not copy recursively from "src-dir" to "dst-dir". src-dir/test: permission denied
    (elixir 1.20.0-rc.4) lib/file.ex:1252: File.cp_r!/3
    iex:1: (file)

As I've mentioned before, I use Guix System (and I'm a maintainer of Erlang and Elixir packages), which is immutable, just like a little bit more popular NixOS, so everything there is in read-only "store", i.e.:

% ls -ld /gnu/store/vwif63v4d5hbna1isr1iaamxqlqjiwdb-erlang-27.3.4.6/lib/erlang/erts-15.2.7.4/bin
dr-xr-xr-x 2 root root 4096 Jan  1  1970 /gnu/store/vwif63v4d5hbna1isr1iaamxqlqjiwdb-erlang-27.3.4.6/lib/erlang/erts-15.2.7.4/bin

Even with fix below applied, some tests fail:

  1) test copy_erts/1 copies to directory (Mix.ReleaseTest)
     test/mix/release_test.exs:664
     ** (File.Error) could not write to file "/home/igor/src/elixir/elixir/lib/mix/tmp/mix_release/_build/dev/rel/demo/erts-15.2.7.4/bin/erl": permission denied
     code: assert copy_erts(release(include_erts: true))
     stacktrace:
       (elixir 1.20.0-rc.4) lib/file.ex:1477: File.write!/3
       (mix 1.20.0-rc.4) lib/mix/release.ex:804: Mix.Release.copy_erts/1
       test/mix/release_test.exs:665: (test)

  2) test copy_app/2 does not copy OTP app if include_erts is false (Mix.ReleaseTest)
     test/mix/release_test.exs:755
     ** (File.Error) could not remove files and directories recursively from "/home/igor/src/elixir/elixir/lib/mix/tmp/mix_release": file already exists
     stacktrace:
       (elixir 1.20.0-rc.4) lib/file.ex:1751: File.rm_rf!/1
       test/mix/release_test.exs:30: Mix.ReleaseTest.__ex_unit_setup_1/1
       test/mix/release_test.exs:7: Mix.ReleaseTest.__ex_unit__/2
...
64) test validates compile_env (Mix.Tasks.ReleaseTest)
     /home/igor/src/elixir/elixir/lib/mix/test/mix/tasks/release_test.exs:542
     ** (EXIT from #PID<0.15884.0>) an exception was raised:
         ** (File.Error) could not write to file "/home/igor/src/elixir/elixir/lib/mix/tmp/Mix.Tasks.ReleaseTest/test validates compile_env/_build/dev/rel/compile_env_config/erts-15.2.7.4/bin/erl": permission denied
             (elixir 1.20.0-rc.4) lib/file.ex:1477: File.write!/3
             (mix 1.20.0-rc.4) lib/mix/release.ex:804: Mix.Release.copy_erts/1
             (mix 1.20.0-rc.4) lib/mix/tasks/release.ex:1391: Mix.Tasks.Release.copy/2
             (elixir 1.20.0-rc.4) lib/task/supervised.ex:105: Task.Supervised.invoke_mfa/2
             (elixir 1.20.0-rc.4) lib/task/supervised.ex:40: Task.Supervised.reply/4
...

Expected behavior

iex(1)> File.cp_r!("src-dir", "dst-dir")
["dst-dir/test", "dst-dir"]

I guess, the problem itself is in lib/elixir/lib/file.ex, function do_cp_r/5. The following changes fix the behaviour:

...
              success when success in [:ok, {:error, :eexist}] ->
                case get_dir_mode(src, dest) do
                  {:ok, dest_fileinfo} ->
                    result =
                      Enum.reduce_while(files, [dest | acc], fn x, acc ->
                        case do_cp_r(
                               Path.join(src, x),
                               Path.join(dest, x),
                               on_conflict,
                               dereference,
                               acc
                             ) do
                          {:error, _, _} = error -> {:halt, error}
                          acc -> {:cont, acc}
                        end
                      end)

                    write_stat(dest, dest_fileinfo)
                    result
...
  defp get_dir_mode(src, dest) do
    with {:ok, dest_fileinfo} <- stat(dest),
         {:ok, src_fileinfo} <- stat(src) do
      {:ok, %{dest_fileinfo | mode: src_fileinfo.mode}}
    end
  end

[josevalim]

This has been fixed in main, see #15286.

[delitrem]

This has been fixed in main, see #15286.

Oops, sorry.

But... in the main branch (last commit is b8a9dc6) tests still fail, I guess this behaviour is related to the change.

  1) test make_sys_config/1 writes sys_config with encoding (Mix.ReleaseTest)
     test/mix/release_test.exs:599
     ** (File.Error) could not remove files and directories recursively from "/home/igor/src/elixir/elixir/lib/mix/tmp/mix_release": file already exists
     stacktrace:
       (elixir 1.20.0-rc.4) lib/file.ex:1747: File.rm_rf!/1
       test/mix/release_test.exs:30: Mix.ReleaseTest.__ex_unit_setup_1/1
       test/mix/release_test.exs:7: Mix.ReleaseTest.__ex_unit__/2
...
 73) test customize include_executables_for and strip_beams (Mix.Tasks.ReleaseTest)
     /home/igor/src/elixir/elixir/lib/mix/test/mix/tasks/release_test.exs:143
     ** (EXIT from #PID<0.25637.0>) an exception was raised:
         ** (File.Error) could not write to file "/home/igor/src/elixir/elixir/lib/mix/tmp/Mix.Tasks.ReleaseTest/test customize include_executables_for and strip_beams/_build/dev/rel/release_test/erts-15.2.7.4/bin/erl": permission denied
             (elixir 1.20.0-rc.4) lib/file.ex:1473: File.write!/3
             (mix 1.20.0-rc.4) lib/mix/release.ex:804: Mix.Release.copy_erts/1
             (mix 1.20.0-rc.4) lib/mix/tasks/release.ex:1391: Mix.Tasks.Release.copy/2
             (elixir 1.20.0-rc.4) lib/task/supervised.ex:105: Task.Supervised.invoke_mfa/2
             (elixir 1.20.0-rc.4) lib/task/supervised.ex:40: Task.Supervised.reply/4
...
Failed: 73 tests