[Python-checkins] closes bpo-39510: Fix use-after-free in BufferedReader.readinto() (GH-18295)
Miss Islington (bot)
webhook-mailer at python.org
Tue Feb 4 16:42:02 EST 2020
https://github.com/python/cpython/commit/30e769382dfb67a68fe8e6bfe8509addb4aa9514
commit: 30e769382dfb67a68fe8e6bfe8509addb4aa9514
branch: 3.8
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-02-04T13:41:55-08:00
summary:
closes bpo-39510: Fix use-after-free in BufferedReader.readinto() (GH-18295)
When called on a closed object, readinto() segfaults on account
of a write to a freed buffer:
==220553== Process terminating with default action of signal 11 (SIGSEGV): dumping core
==220553== Access not within mapped region at address 0x2A
==220553== at 0x48408A0: memmove (vg_replace_strmem.c:1272)
==220553== by 0x58DB0C: _buffered_readinto_generic (bufferedio.c:972)
==220553== by 0x58DCBA: _io__Buffered_readinto_impl (bufferedio.c:1053)
==220553== by 0x58DCBA: _io__Buffered_readinto (bufferedio.c.h:253)
Reproducer:
reader = open ("/dev/zero", "rb")
_void = reader.read (42)
reader.close ()
reader.readinto (bytearray (42)) GH-GH-GH- BANG!
The problem exists since 2012 when commit dc469454ec added code
to free the read buffer on close().
Signed-off-by: Philipp Gesang <philipp.gesang at intra2net.com>
(cherry picked from commit cb1c0746f277052e45a60d6c436a765e34722821)
Co-authored-by: Philipp Gesang <phg at phi-gamma.net>
files:
A Misc/NEWS.d/next/Core and Builtins/2020-02-04-10-27-41.bpo-39510.PMIh-f.rst
M Lib/test/test_io.py
M Modules/_io/bufferedio.c
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 50459e0792962..bea4342e7f0f9 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -735,6 +735,11 @@ def test_read_closed(self):
file.seek(0)
file.close()
self.assertRaises(ValueError, file.read)
+ with self.open(support.TESTFN, "rb") as f:
+ file = self.open(f.fileno(), "rb", closefd=False)
+ self.assertEqual(file.read()[:3], b"egg")
+ file.close()
+ self.assertRaises(ValueError, file.readinto, bytearray(1))
def test_no_closefd_with_filename(self):
# can't use closefd in combination with a file name
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-02-04-10-27-41.bpo-39510.PMIh-f.rst b/Misc/NEWS.d/next/Core and Builtins/2020-02-04-10-27-41.bpo-39510.PMIh-f.rst
new file mode 100644
index 0000000000000..9a38e4ab76228
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-02-04-10-27-41.bpo-39510.PMIh-f.rst
@@ -0,0 +1 @@
+Fix segfault in ``readinto()`` method on closed BufferedReader.
diff --git a/Modules/_io/bufferedio.c b/Modules/_io/bufferedio.c
index 8e8ff97ff8c67..ad7a8c9d26427 100644
--- a/Modules/_io/bufferedio.c
+++ b/Modules/_io/bufferedio.c
@@ -965,6 +965,7 @@ _buffered_readinto_generic(buffered *self, Py_buffer *buffer, char readinto1)
PyObject *res = NULL;
CHECK_INITIALIZED(self)
+ CHECK_CLOSED(self, "readinto of closed file")
n = Py_SAFE_DOWNCAST(READAHEAD(self), Py_off_t, Py_ssize_t);
if (n > 0) {
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