diff options
Diffstat (limited to 'Modules/mmapmodule.c')
| -rw-r--r-- | Modules/mmapmodule.c | 16 |
1 files changed, 13 insertions, 3 deletions
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 @@ static PyObject * 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 @@ mmap_read_method(mmap_object *self, 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; |