Date: Thu, 24 May 2001 16:53:33 +0930 From: Greg Lehey <grog@lemis.com> To: doug@safeport.com Cc: freebsd-questions@FreeBSD.ORG Subject: Re: /dev/io: Operation not permitted Message-ID: <20010524165332.H81537@wantadilla.lemis.com> In-Reply-To: <Pine.BSF.4.21.0105231727170.6227-100000@pemaquid.safeport.com>; from doug@safeport.com on Wed, May 23, 2001 at 05:40:20PM -0400 References: <Pine.BSF.4.21.0105231727170.6227-100000@pemaquid.safeport.com>
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On Wednesday, 23 May 2001 at 17:40:20 -0400, doug@safeport.com wrote: > 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. This is correct. You can't read from or write to /dev/io. It's intended for ioctl calls only. The relevant code is in sys/i386/i386/mem.c. > The reason I care is XFree86 -configure fail with the same > error. This system was installed from ftp.freebsd.org on 5/20 As I've said in private mail, I suspect you're looking in the wrong place here. Greg -- When replying to this message, please copy the original recipients. If you don't, I may ignore the reply. For more information, see http://www.lemis.com/questions.html Finger grog@lemis.com for PGP public key See complete headers for address and phone numbers To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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