correct logic when pos is after the string #10467
diff --git a/Modules/_io/bytesio.c b/Modules/_io/bytesio.c
index c565404..b40513f 100644
--- a/Modules/_io/bytesio.c
+++ b/Modules/_io/bytesio.c
@@ -430,15 +430,20 @@
bytesio_readinto(bytesio *self, PyObject *buffer)
{
void *raw_buffer;
- Py_ssize_t len;
+ Py_ssize_t len, n;
CHECK_CLOSED(self);
if (PyObject_AsWriteBuffer(buffer, &raw_buffer, &len) == -1)
return NULL;
- if (self->pos + len > self->string_size)
- len = self->string_size - self->pos;
+ /* adjust invalid sizes */
+ n = self->string_size - self->pos;
+ if (len > n) {
+ len = n;
+ if (len < 0)
+ len = 0;
+ }
memcpy(raw_buffer, self->buf + self->pos, len);
assert(self->pos + len < PY_SSIZE_T_MAX);