Date: Wed, 23 May 2001 17:40:20 -0400 (EDT) From: <doug@safeport.com> To: freebsd-questions@FreeBSD.ORG Subject: /dev/io: Operation not permitted Message-ID: <Pine.BSF.4.21.0105231727170.6227-100000@pemaquid.safeport.com>
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I have a 4.3 system where root can not write to /dev/io. I assume I have screwed
something up but I am told the permissions:
crw------- 1 root wheel 2, 14 May 9 19:56 /dev/io
are okay and indeed matches my other systems. The man page io(4) would suggest
this is hard to do:
DESCRIPTION
The special file /dev/io is a controlled security hole that allows a pro-
cess to gain I/O privileges (which are normally reserved for kernel-
internal code). Any process that holds a file descriptor on /dev/io open
will get its IOPL bits in the flag register set, thus allowing it to per-
form direct I/O operations. This can be useful in order to write user-
land programs that handle some hardware directly.
The entire access control is handled by the file access permissions of
/dev/io, so care should be taken in granting rights for this device.
Note that even read/only access will grant the full I/O privileges.
However:
Last login: Tue May 22 18:21:34 2001 from pemaquid.boltsys
Copyright (c) 1980, 1983, 1986, 1988, 1990, 1991, 1993, 1994
The Regents of the University of California. All rights reserved.
FreeBSD 4.3-RELEASE (GENERIC) #0: Sat Apr 21 10:54:49 GMT 2001
Welcome to FreeBSD!
mneme:~> su
Password:
mneme:/home/doug# echo "poo I say" > /dev/io
/dev/io: Operation not permitted.
__________________________________________
The reason I care is XFree86 -configure fail with the same error. This system
was installed from ftp.freebsd.org on 5/20
_____
Douglas Denault
doug@safeport.com
Voice: 301-469-8766
Fax: 301-469-0601
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