[ruby/stringio] Cannot read into the underlying string

Fix https://hackerone.com/reports/3716987

https://github.com/ruby/stringio/commit/4ed1d6b7cf

1 files changed, 3 insertions, 0 deletions

diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index aca250a85a..0f61245a8a 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -765,6 +765,8 @@ class TestStringIO < Test::Unit::TestCase
     s = ""
     f.read(nil, s)
     assert_equal(Encoding::ASCII_8BIT, s.encoding, bug20418)
+
+    assert_raise(ArgumentError) {f.read(1, f.string)}
   end
 
   def test_readpartial
@@ -830,6 +832,7 @@ class TestStringIO < Test::Unit::TestCase
 
     assert_raise(EOFError) { f.pread(1, 5) }
     assert_raise(ArgumentError) { f.pread(-1, 0) }
+    assert_raise(ArgumentError) { f.pread(0, 0, f.string) }
     assert_raise(Errno::EINVAL) { f.pread(3, -1) }
     assert_raise(Errno::EINVAL) { f.pread(0, -1) }
     assert_raise(IOError) { StringIO.new(nil, "w").pread(3, 0) }