bpo-34879: Fix a possible null pointer dereference in bytesobject.c (GH-9683)

ZackerySpytz · serhiy-storchaka · commit 96c593279400 · 2018-10-03T09:01:30.000+03:00
formatfloat() was not checking if PyBytes_FromStringAndSize()
failed, which could lead to a null pointer dereference in
_PyBytes_FormatEx().
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-10-02-22-55-11.bpo-34879.7VNH2a.rst b/Misc/NEWS.d/next/Core and Builtins/2018-10-02-22-55-11.bpo-34879.7VNH2a.rst
@@ -0,0 +1,2 @@
+Fix a possible null pointer dereference in bytesobject.c.  Patch by Zackery
+Spytz.
diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
@@ -448,7 +448,7 @@ formatfloat(PyObject *v, int flags, int prec, int type,
     result = PyBytes_FromStringAndSize(p, len);
     PyMem_Free(p);
     *p_result = result;
-    return str;
+    return result != NULL ? str : NULL;
 }
 
 static PyObject *

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Fix a possible null pointer dereference in bytesobject.c. Patch by Zackery`
	`2`	`+Spytz.`
Original file line number	Diff line number	Diff line change
`@@ -448,7 +448,7 @@ formatfloat(PyObject *v, int flags, int prec, int type,`
`448`	`448`	`result = PyBytes_FromStringAndSize(p, len);`
`449`	`449`	`PyMem_Free(p);`
`450`	`450`	`*p_result = result;`
`451`		`- return str;`
	`451`	`+ return result != NULL ? str : NULL;`
`452`	`452`	`}`
`453`	`453`
`454`	`454`	`static PyObject *`