bpo-38730: Replace strncpy in import.c with memcpy. (GH-17633)

benjaminp · web-flow · commit 052f47ef5cc3 · 2019-12-16T16:39:57.000-08:00
In all these cases, we know the exact length we want copied, so memcpy is the right function to use.
diff --git a/Python/import.c b/Python/import.c
@@ -2456,7 +2456,7 @@ get_parent(PyObject *globals, char *buf, Py_ssize_t *p_buflen, int level)
                                 "Module name too long");
                 return NULL;
             }
-            strncpy(buf, start, len);
+            memcpy(buf, start, len);
             buf[len] = '\0';
             pkgname = PyString_FromString(buf);
             if (pkgname == NULL) {
@@ -2554,7 +2554,7 @@ load_next(PyObject *mod, PyObject *altmod, char **p_name, char *buf,
                         "Module name too long");
         return NULL;
     }
-    strncpy(p, name, len);
+    memcpy(p, name, len);
     p[len] = '\0';
     *p_buflen = p+len-buf;
 
@@ -2568,7 +2568,7 @@ load_next(PyObject *mod, PyObject *altmod, char **p_name, char *buf,
                 Py_DECREF(result);
                 return NULL;
             }
-            strncpy(buf, name, len);
+            memcpy(buf, name, len);
             buf[len] = '\0';
             *p_buflen = len;
         }

Original file line number	Diff line number	Diff line change
`@@ -2456,7 +2456,7 @@ get_parent(PyObject globals, char buf, Py_ssize_t *p_buflen, int level)`
`2456`	`2456`	`"Module name too long");`
`2457`	`2457`	`return NULL;`
`2458`	`2458`	`}`
`2459`		`- strncpy(buf, start, len);`
	`2459`	`+ memcpy(buf, start, len);`
`2460`	`2460`	`buf[len] = '\0';`
`2461`	`2461`	`pkgname = PyString_FromString(buf);`
`2462`	`2462`	`if (pkgname == NULL) {`
`@@ -2554,7 +2554,7 @@ load_next(PyObject mod, PyObject altmod, char *p_name, char buf,`
`2554`	`2554`	`"Module name too long");`
`2555`	`2555`	`return NULL;`
`2556`	`2556`	`}`
`2557`		`- strncpy(p, name, len);`
	`2557`	`+ memcpy(p, name, len);`
`2558`	`2558`	`p[len] = '\0';`
`2559`	`2559`	`*p_buflen = p+len-buf;`
`2560`	`2560`
`@@ -2568,7 +2568,7 @@ load_next(PyObject mod, PyObject altmod, char *p_name, char buf,`
`2568`	`2568`	`Py_DECREF(result);`
`2569`	`2569`	`return NULL;`
`2570`	`2570`	`}`
`2571`		`- strncpy(buf, name, len);`
	`2571`	`+ memcpy(buf, name, len);`
`2572`	`2572`	`buf[len] = '\0';`
`2573`	`2573`	`*p_buflen = len;`
`2574`	`2574`	`}`