Issue #9550: a BufferedReader could issue an additional read when the
original read request had been satisfied, which can block indefinitely
when the underlying raw IO channel is e.g. a socket. Report and original
patch by Jason V. Miller.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 1dd1ec4..4678da9 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -1383,7 +1383,10 @@
self->pos = 0;
self->raw_pos = 0;
self->read_end = 0;
- while (self->read_end < self->buffer_size) {
+ /* NOTE: when the read is satisfied, we avoid issuing any additional
+ reads, which could block indefinitely (e.g. on a socket).
+ See issue #9550. */
+ while (remaining > 0 && self->read_end < self->buffer_size) {
Py_ssize_t r = _bufferedreader_fill_buffer(self);
if (r == -1)
goto error;