Bugtraq mailing list archives
Re: HP-UX setprivgrp()
From: dsiebert () icaen uiowa edu (dsiebert () icaen uiowa edu)
Date: Fri, 8 Nov 1996 20:31:01 -0600
On Thu, 07 Nov 1996 22:51:54 +0100, Valdis Kletnieks (Valdis.Kletnieks () vt edu) wrote:Don't bother trying, system calls are atomic... but you can use thisHave you in fact verified that this is guaranteed true on a multiprocessor system? Remember that the other side(s) of the machine can still be running, and the kernel needs to explicitly lock out any activity that it doesn't want to be seen. Doing this in an efficient manner is in fact the single hardest thing with building a good MP system - you have to minimize the locked sections of code so the other CPUs can proceed as often as possible. I haven't checked a Unix kernel, but IBM's VM operating system has on the order of 200 or so different locks to provide as fine granularity as needed. Of course, sometimes the lock turns out to be a bit TOO granular.. ;)
The kernel locking doesn't matter here, the inode itself is locked by the OS while being modified, so another CPU would wait for the first to be done, even if the kernel was fully was threaded so the chown and chmod calls were able to run in parallel. I know its this way in HP-UX, I suspect it is this way in all Unixes. If you don't want your HP-UX system to allow users to give away files (which is the standard SysV behavior) create a file called /etc/privgroup with "-g" in it, and this will be used as an argument to a setprivgrp call on startup which will prevent this. -- Douglas Siebert Director of Computing Facilities douglas-siebert () uiowa edu Division of Mathematical Sciences, U of Iowa Ack! My reality check just bounced!!
Current thread:
- HP-UX setprivgrp() Eduardo E. Silva (Nov 07)
- <Possible follow-ups>
- Re: HP-UX setprivgrp() Dominique Quatravaux (Nov 07)
- Re: HP-UX setprivgrp() Valdis.Kletnieks () vt edu (Nov 08)
- Bos: Firewall-1 ping bug...? Eduardo E. Silva (Nov 08)
- Re: HP-UX setprivgrp() dsiebert () icaen uiowa edu (Nov 08)
- Syslogd and Solaris 2.4 Denis Campeau (Nov 08)
- Syslogd and Solaris 2.4 Scriptors of DOOM (Nov 09)
- CIAC Bulletin H-03: HP-UX suid Vulnerabilities Bill Orvis (Nov 09)
- CIAC Bulletin F-04: HP-UX Ping Vulnerability Bill Orvis (Nov 09)
- Re: HP-UX setprivgrp() Valdis.Kletnieks () vt edu (Nov 08)