py/objdeque: Protect against negative maxlen in deque constructor.

Otherwise passing -1 as maxlen will lead to a zero allocation and
subsequent unbound buffer overflow in deque.append() because i_put is
allowed to grow without bound.

1 files changed, 6 insertions, 0 deletions

diff --git a/tests/basics/deque1.py b/tests/basics/deque1.py
index 6b5669c45..19966fcb0 100644
--- a/tests/basics/deque1.py
+++ b/tests/basics/deque1.py
@@ -55,6 +55,12 @@ d.append(4)
 d.append(5)
 print(d.popleft(), d.popleft())
 
+# Negative maxlen is not allowed
+try:
+    deque((), -1)
+except ValueError:
+    print("ValueError")
+
 # Unsupported unary op
 try:
     ~d