When parsing sockaddr_un structures returned by accept(), etc.,
only examine bytes up to supplied addrlen and do not require null
termination.

diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -963,18 +963,23 @@ makesockaddr(int sockfd, struct sockaddr
 #if defined(AF_UNIX)
 	case AF_UNIX:
 	{
+		Py_ssize_t len, splen;
 		struct sockaddr_un *a = (struct sockaddr_un *) addr;
+		splen = addrlen - offsetof(struct sockaddr_un, sun_path);
 #ifdef linux
-		if (a->sun_path[0] == 0) {  /* Linux abstract namespace */
-			addrlen -= offsetof(struct sockaddr_un, sun_path);
-			return PyBytes_FromStringAndSize(a->sun_path, addrlen);
+		if (splen > 0 && a->sun_path[0] == 0) {
+			/* Linux abstract namespace */
+			return PyBytes_FromStringAndSize(a->sun_path, splen);
 		}
 		else
 #endif /* linux */
 		{
-			/* regular NULL-terminated string */
-			return PyUnicode_FromString(a->sun_path);
+			/* String, up to null terminator if present */
+			for (len = 0; len < splen && a->sun_path[len] != 0;
+			     len++)
+				;
 		}
+		return PyUnicode_FromStringAndSize(a->sun_path, len);
 	}
 #endif /* AF_UNIX */