From 9fa70ff733c6c962624ae82a46a67a22caebb9b0 Mon Sep 17 00:00:00 2001
From: Mark Wooding <mdw@distorted.org.uk>
Date: Sat, 12 Oct 2019 21:07:05 +0100
Subject: [PATCH] buffer.c (wbmeth_putblkN): Check input block size.

Otherwise the C code fails an assertion.
---
 buffer.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/buffer.c b/buffer.c
index 17d7caa..27eafd1 100644
--- a/buffer.c
+++ b/buffer.c
@@ -406,16 +406,20 @@ static PyObject *wbmeth_put(PyObject *me, PyObject *arg)
   }
 DOUINTCONV(WBMETH_PUTU_)
 
+#define MASKz 0
 #define SZ_z 1
 #define WBMETH_PUTBLK_(n, W, w)						\
   static PyObject *wbmeth_putblk##w(PyObject *me, PyObject *arg)	\
   {									\
     char *p;								\
     Py_ssize_t sz;							\
-    if (!PyArg_ParseTuple(arg, "s#:putblk" #w, &p, &sz)) return (0);	\
+    if (!PyArg_ParseTuple(arg, "s#:putblk" #w, &p, &sz)) goto end;	\
+    if (MASK##W && sz > MASK##W) VALERR("too large");			\
     ensure(me, sz + SZ_##n);						\
     buf_putmem##w(BUF_B(me), p, sz); assert(BOK(BUF_B(me)));		\
     RETURN_ME;								\
+  end:									\
+    return (0);								\
   }
 BUF_DOSUFFIXES(WBMETH_PUTBLK_)
 
-- 
2.11.0