ropes: Fix a buffer overflow in `RopeBuffer.add`.

Signed-off-by: Jean-Christophe Beaupré <jcbrinfo@users.noreply.github.com>

diff --git a/lib/standard/ropes.nit b/lib/standard/ropes.nit
index 9ef2f4d..d41c021 100644 (file)
--- a/lib/standard/ropes.nit
+++ b/lib/standard/ropes.nit
@@ -337,14 +337,13 @@ class RopeBuffer
 
        redef fun add(c) do
                var rp = rpos
-               length += 1
-               ns[rp] = c
-               rp += 1
-               if rp == buf_size then
-                       rpos = rp
+               if rp >= buf_size then
                        dump_buffer
                        rp = 0
                end
+               ns[rp] = c
+               rp += 1
+               length += 1
                rpos = rp
        end
 

diff --git a/tests/sav/test_ropes_buffer_add_overflow.res b/tests/sav/test_ropes_buffer_add_overflow.res
new file mode 100644 (file)
index 0000000..e69de29

diff --git a/tests/test_ropes_buffer_add_overflow.nit b/tests/test_ropes_buffer_add_overflow.nit
new file mode 100644 (file)
index 0000000..6482b0e
--- /dev/null
+++ b/tests/test_ropes_buffer_add_overflow.nit
@@ -0,0 +1,28 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Checks that `RopeBuffer.add` does not makes the internal buffer overflow.
+#
+# Note: In order to help repoducibility, this test read an private attribute of
+# the buffer.
+module test_ropes_buffer_add_overflow
+
+import standard
+intrude import ropes
+
+var buffer = new RopeBuffer
+
+buffer.append("x" * maxlen)
+buffer.add 'y'
+assert buffer.rpos <= maxlen else print "{buffer.rpos} > {maxlen}"