diff options
| -rw-r--r-- | Lib/test/test_io.py | 24 | ||||
| -rw-r--r-- | Misc/ACKS | 1 | ||||
| -rw-r--r-- | Misc/NEWS | 5 | ||||
| -rw-r--r-- | Modules/_io/bufferedio.c | 5 |
4 files changed, 34 insertions, 1 deletions
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py index f6175c8..8241bbe 100644 --- a/Lib/test/test_io.py +++ b/Lib/test/test_io.py @@ -51,12 +51,14 @@ class MockRawIO: self._read_stack = list(read_stack) self._write_stack = [] self._reads = 0 + self._extraneous_reads = 0 def read(self, n=None): self._reads += 1 try: return self._read_stack.pop(0) except: + self._extraneous_reads += 1 return b"" def write(self, b): @@ -87,6 +89,7 @@ class MockRawIO: try: data = self._read_stack[0] except IndexError: + self._extraneous_reads += 1 return 0 if data is None: del self._read_stack[0] @@ -822,6 +825,27 @@ class BufferedReaderTest(unittest.TestCase, CommonBufferedTests): self.assertRaises(IOError, bufio.seek, 0) self.assertRaises(IOError, bufio.tell) + def test_no_extraneous_read(self): + # Issue #9550; when the raw IO object has satisfied the read request, + # we should not issue any additional reads, otherwise it may block + # (e.g. socket). + bufsize = 16 + for n in (2, bufsize - 1, bufsize, bufsize + 1, bufsize * 2): + rawio = self.MockRawIO([b"x" * n]) + bufio = self.tp(rawio, bufsize) + self.assertEqual(bufio.read(n), b"x" * n) + # Simple case: one raw read is enough to satisfy the request. + self.assertEqual(rawio._extraneous_reads, 0, + "failed for {}: {} != 0".format(n, rawio._extraneous_reads)) + # A more complex case where two raw reads are needed to satisfy + # the request. + rawio = self.MockRawIO([b"x" * (n - 1), b"x"]) + bufio = self.tp(rawio, bufsize) + self.assertEqual(bufio.read(n), b"x" * n) + self.assertEqual(rawio._extraneous_reads, 0, + "failed for {}: {} != 0".format(n, rawio._extraneous_reads)) + + class CBufferedReaderTest(BufferedReaderTest): tp = io.BufferedReader @@ -524,6 +524,7 @@ Trent Mick Aristotelis Mikropoulos Damien Miller Chad Miller +Jason V. Miller Jay T. Miller Roman Milner Andrii V. Mishkovskyi @@ -93,6 +93,11 @@ C-API Library ------- +- Issue #9550: a BufferedReader could issue an additional read when the + original read request had been satisfied, which could block indefinitely + when the underlying raw IO channel was e.g. a socket. Report and original + patch by Jason V. Miller. + - Issue #6915: Under Windows, os.listdir() didn't release the Global Interpreter Lock around all system calls. Original patch by Ryan Kelly. diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c index c0c3acc..d8c1e65 100644 --- a/Modules/_io/bufferedio.c +++ b/Modules/_io/bufferedio.c @@ -1379,7 +1379,10 @@ _bufferedreader_read_generic(buffered *self, Py_ssize_t n) 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; |