Issue #6344: Fixed a crash of mmap.read() when passed a negative argument.
Reviewed by Amaury Forgeot d'Arc.
diff --git a/Misc/NEWS b/Misc/NEWS
index 5ab68bc..d021fd2 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@
Core and Builtins
-----------------
+- Issue #6344: Fixed a crash of mmap.read() when passed a negative argument.
+
- Issue #4856: Remove checks for win NT.
- Issue #2016: Fixed a crash in a corner case where the dictionary of keyword
diff --git a/Modules/mmapmodule.c b/Modules/mmapmodule.c
index e1970cb..5e0b3ad 100644
--- a/Modules/mmapmodule.c
+++ b/Modules/mmapmodule.c
@@ -232,7 +232,7 @@
mmap_read_method(mmap_object *self,
PyObject *args)
{
- Py_ssize_t num_bytes;
+ Py_ssize_t num_bytes, n;
PyObject *result;
CHECK_VALID(NULL);
@@ -240,8 +240,18 @@
return(NULL);
/* silently 'adjust' out-of-range requests */
- if (num_bytes > self->size - self->pos) {
- num_bytes -= (self->pos+num_bytes) - self->size;
+ assert(self->size >= self->pos);
+ n = self->size - self->pos;
+ /* The difference can overflow, only if self->size is greater than
+ * PY_SSIZE_T_MAX. But then the operation cannot possibly succeed,
+ * because the mapped area and the returned string each need more
+ * than half of the addressable memory. So we clip the size, and let
+ * the code below raise MemoryError.
+ */
+ if (n < 0)
+ n = PY_SSIZE_T_MAX;
+ if (num_bytes < 0 || num_bytes > n) {
+ num_bytes = n;
}
result = Py_BuildValue("s#", self->data+self->pos, num_bytes);
self->pos += num_bytes;