ex vito
2016-12-28 03:15:58 UTC
Dear all,
While working on http://twistedmatrix.com/trac/ticket/8912 and the associated PR at https://github.com/twisted/twisted/pull/647 I hit a segmentation fault on a test I was preparing.
I think narrowed it down Linux + Python 2, but I'm not 100% sure. Can anyone please confirm the code below segfaults on such environment? For completeness, from my tests, it works fine on Linux + Python 3, and fails with socket.error/OSError on Mac OS 10.9.5 + Python 2/3. No BSDs at hand to try out...
As far as I can tell, no code in Twisted uses sendmsg in the way the code is using it. However, twisted.python.sendmsg is a public API so someone somewhere may hit this like I just did.
Other than looking for confirmation, I have a fix which I included two isolated commits in the PR. Twisted project members: if this is confirmed, maybe a ticket should be created in Trac and an independent PR created, correct?
Thanks in advance for any input.
Regards,
--
exvito
-[ cut here ]----------------------------------------------------------------------
import os
import socket
import struct
import sys
from twisted.python import sendmsg
if __name__ == '__main__':
# This code segfaults when running with twisted/trunk commit
# 98a3df200968b78bd3b985dfd4fb10a5b415d6fc on Linux Python 2
# due to a bug in src/twisted/python/_sendmsg.c and glibc's
# CMSG_NXTHDR implementation.
# get connected sockets
s1, s2 = socket.socketpair(socket.AF_UNIX)
# two CMSGs in ancillary data (no segfault with just one)
ancillary = [
(socket.SOL_SOCKET, sendmsg.SCM_RIGHTS, struct.pack('i', s1.fileno())),
(socket.SOL_SOCKET, sendmsg.SCM_RIGHTS, struct.pack('i', s2.fileno())),
]
expected = {
2: 'Expecting to segfault.',
3: 'Should not segfault.',
}
print expected.get(sys.version_info.major, 'Unexpected Python version.')
retval = sendmsg.sendmsg(s1, data=b'some data', ancillary=ancillary)
print 'Did not segfault.'
-[ cut here ]----------------------------------------------------------------------
While working on http://twistedmatrix.com/trac/ticket/8912 and the associated PR at https://github.com/twisted/twisted/pull/647 I hit a segmentation fault on a test I was preparing.
I think narrowed it down Linux + Python 2, but I'm not 100% sure. Can anyone please confirm the code below segfaults on such environment? For completeness, from my tests, it works fine on Linux + Python 3, and fails with socket.error/OSError on Mac OS 10.9.5 + Python 2/3. No BSDs at hand to try out...
As far as I can tell, no code in Twisted uses sendmsg in the way the code is using it. However, twisted.python.sendmsg is a public API so someone somewhere may hit this like I just did.
Other than looking for confirmation, I have a fix which I included two isolated commits in the PR. Twisted project members: if this is confirmed, maybe a ticket should be created in Trac and an independent PR created, correct?
Thanks in advance for any input.
Regards,
--
exvito
-[ cut here ]----------------------------------------------------------------------
import os
import socket
import struct
import sys
from twisted.python import sendmsg
if __name__ == '__main__':
# This code segfaults when running with twisted/trunk commit
# 98a3df200968b78bd3b985dfd4fb10a5b415d6fc on Linux Python 2
# due to a bug in src/twisted/python/_sendmsg.c and glibc's
# CMSG_NXTHDR implementation.
# get connected sockets
s1, s2 = socket.socketpair(socket.AF_UNIX)
# two CMSGs in ancillary data (no segfault with just one)
ancillary = [
(socket.SOL_SOCKET, sendmsg.SCM_RIGHTS, struct.pack('i', s1.fileno())),
(socket.SOL_SOCKET, sendmsg.SCM_RIGHTS, struct.pack('i', s2.fileno())),
]
expected = {
2: 'Expecting to segfault.',
3: 'Should not segfault.',
}
print expected.get(sys.version_info.major, 'Unexpected Python version.')
retval = sendmsg.sendmsg(s1, data=b'some data', ancillary=ancillary)
print 'Did not segfault.'
-[ cut here ]----------------------------------------------------------------------