bpo-24618: Add a check in the code constructor. (GH-8283)
Check that the size of the varnames tuple is enough at least for all arguments.
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-07-14-14-01-37.bpo-24618.iTKjD_.rst b/Misc/NEWS.d/next/Core and Builtins/2018-07-14-14-01-37.bpo-24618.iTKjD_.rst
new file mode 100644
index 0000000..180b565
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-07-14-14-01-37.bpo-24618.iTKjD_.rst
@@ -0,0 +1,2 @@
+Fixed reading invalid memory when create the code object with too small
+varnames tuple or too large argument counts.
diff --git a/Objects/codeobject.c b/Objects/codeobject.c
index aa373a0..b07667c 100644
--- a/Objects/codeobject.c
+++ b/Objects/codeobject.c
@@ -103,7 +103,7 @@
{
PyCodeObject *co;
Py_ssize_t *cell2arg = NULL;
- Py_ssize_t i, n_cellvars;
+ Py_ssize_t i, n_cellvars, n_varnames, total_args;
/* Check argument types */
if (argcount < 0 || kwonlyargcount < 0 || nlocals < 0 ||
@@ -138,10 +138,22 @@
flags &= ~CO_NOFREE;
}
+ n_varnames = PyTuple_GET_SIZE(varnames);
+ if (argcount <= n_varnames && kwonlyargcount <= n_varnames) {
+ /* Never overflows. */
+ total_args = (Py_ssize_t)argcount + (Py_ssize_t)kwonlyargcount +
+ ((flags & CO_VARARGS) != 0) + ((flags & CO_VARKEYWORDS) != 0);
+ }
+ else {
+ total_args = n_varnames + 1;
+ }
+ if (total_args > n_varnames) {
+ PyErr_SetString(PyExc_ValueError, "code: varnames is too small");
+ return NULL;
+ }
+
/* Create mapping between cells and arguments if needed. */
if (n_cellvars) {
- Py_ssize_t total_args = argcount + kwonlyargcount +
- ((flags & CO_VARARGS) != 0) + ((flags & CO_VARKEYWORDS) != 0);
bool used_cell2arg = false;
cell2arg = PyMem_NEW(Py_ssize_t, n_cellvars);
if (cell2arg == NULL) {