New submission from Grzegorz Kulewski <[email protected]>:
Hello,
It looks like something is broken in ioctl in 3.2 when the supplied (mutable)
bytearray is exactly 1024 bytes long - the result is not copied into the buffer
after the ioctl succedes:
def open_tuntap(type, name):
TUN_TYPE = {
'TUN' : 0x0001,
'TAP' : 0x0002
}
TUNSETIFF = 0x400454ca
dev = os.open('/dev/net/tun', os.O_RDWR)
buf = bytearray(SET_LEN_HERE)
name = name[:16]
buf[:len(name)] = name
buf[16:18] = TUN_TYPE[type].to_bytes(2, sys.byteorder)
fcntl.ioctl(dev, TUNSETIFF, buf, True)
print(buf)
print(len(buf))
open_tuntap('TAP', b'madtun%d')
Now try it with SET_LEN_HERE = 1024, 1023, 1025 and any other values. For <
1024 it copies to the static buffer and back, for > 1024 it operates on the
buffer itself (hopefully) and for 1024 it ignores the modified buffer
completely. It's probably some corner case bug.
The example was tested under Linux 2.6.35.
Python 3.2a1+ (py3k:84054, Sep 3 2010, 01:45:35)
[GCC 4.4.2] on linux2
----------
components: Library (Lib)
messages: 115467
nosy: gkulewski
priority: normal
severity: normal
status: open
title: ioctl mutable buffer copying problem
type: behavior
versions: Python 3.2
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Python tracker <[email protected]>
<http://bugs.python.org/issue9758>
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