closes bpo-41533: Fix a potential memory leak when allocating a stack (pythonGH-21847)

tontinton · web-flow · commit 75c80b0bda89 · 2020-08-29T23:53:08.000-05:00
Free the stack allocated in va_build_stack if do_mkstack fails
and the stack is not a small_stack
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-08-12-20-29-57.bpo-41533.4pcVAc.rst b/Misc/NEWS.d/next/Core and Builtins/2020-08-12-20-29-57.bpo-41533.4pcVAc.rst
@@ -0,0 +1,2 @@
+Free the stack allocated in ``va_build_stack`` if ``do_mkstack`` fails and
+the stack is not a ``small_stack``.
diff --git a/Python/modsupport.c b/Python/modsupport.c
@@ -622,6 +622,9 @@ va_build_stack(PyObject **small_stack, Py_ssize_t small_stack_len,
     va_end(lva);
 
     if (res < 0) {
+        if (stack != small_stack) {
+            PyMem_Free(stack);
+        }
         return NULL;
     }
 

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	+Free the stack allocated in ``va_build_stack`` if ``do_mkstack`` fails and
	`2`	+the stack is not a ``small_stack``.
Original file line number	Diff line number	Diff line change
`@@ -622,6 +622,9 @@ va_build_stack(PyObject **small_stack, Py_ssize_t small_stack_len,`
`622`	`622`	`va_end(lva);`
`623`	`623`
`624`	`624`	`if (res < 0) {`
	`625`	`+ if (stack != small_stack) {`
	`626`	`+ PyMem_Free(stack);`
	`627`	`+ }`
`625`	`628`	`return NULL;`
`626`	`629`	`}`
`627`	`630`