fix(LDAPObject): Prevent memory errors in attrs_from_List

jkoeniger · tiran · jkoeniger · commit 0859ed8186b8 · 2024-01-30T09:54:41.000+01:00
Function `PySequence_Length` can return -1 on iterables like `dict`.
The following PyMem_NEW still succeeds due `PyMem_NEW(char *, -1 + 1)`
being equivalent to `char** PyMem_Malloc(1)`, which then can result in a
segmentation fault later on.

Solution: Use `seq` and `PySequence_Size` to determine the size of
the sequence. This way any iterable which contains only strings can be used.

Co-authored-by: Christian Heimes &lt;christian@python.org&gt;
diff --git a/Modules/LDAPObject.c b/Modules/LDAPObject.c
@@ -288,7 +288,10 @@ attrs_from_List(PyObject *attrlist, char ***attrsp)
         if (seq == NULL)
             goto error;
 
-        len = PySequence_Length(attrlist);
+	len = PySequence_Size(seq);
+	if (len == -1) {
+	    goto error;
+	}
 
         attrs = PyMem_NEW(char *, len + 1);
 
