From: stratakis <cstratak@redhat.com>
Date: Wed, 8 Jul 2020 20:39:41 +0000 (+0200)
Subject: bpo-41175: Guard against a NULL pointer dereference within bytearrayobject (GH-21240)
X-Git-Tag: v3.10.0a1~421
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=61fc23ca106bc82955b0e59d1ab42285b94899e2;p=thirdparty%2FPython%2Fcpython.git

bpo-41175: Guard against a NULL pointer dereference within bytearrayobject (GH-21240)

The issue is triggered by the bytearray() + bytearray() operation.

Detected by GCC 10 static analysis tool.
---

diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-06-30-20-17-31.bpo-41175.acJoXB.rst b/Misc/NEWS.d/next/Core and Builtins/2020-06-30-20-17-31.bpo-41175.acJoXB.rst
new file mode 100644
index 000000000000..844fb804c0c8
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-06-30-20-17-31.bpo-41175.acJoXB.rst	
@@ -0,0 +1,2 @@
+Guard against a NULL pointer dereference within bytearrayobject triggered by
+the ``bytearray() + bytearray()`` operation.
diff --git a/Objects/bytearrayobject.c b/Objects/bytearrayobject.c
index 83c79b200a0a..703506193309 100644
--- a/Objects/bytearrayobject.c
+++ b/Objects/bytearrayobject.c
@@ -266,7 +266,9 @@ PyByteArray_Concat(PyObject *a, PyObject *b)
 
     result = (PyByteArrayObject *) \
         PyByteArray_FromStringAndSize(NULL, va.len + vb.len);
-    if (result != NULL) {
+    // result->ob_bytes is NULL if result is an empty string:
+    // if va.len + vb.len equals zero.
+    if (result != NULL && result->ob_bytes != NULL) {
         memcpy(result->ob_bytes, va.buf, va.len);
         memcpy(result->ob_bytes + va.len, vb.buf, vb.len);
     }