Messages in this thread | | | Subject | Re: only root has acces to /dev/mem ? | Date | Tue, 14 Sep 1999 08:14:02 +0200 (MEST) | From | (Rogier Wolff) |
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Alan Cox wrote: > > sine i am using 2.2.12 i had no permissions to write on /dev/mem > > i belong to the group kmem who has +rw on it i cann't write > > when i chown it the user cann't still write on it > > only root can?? > > was it a security bug or so?? > > Tightening rather than anything else. You need the RAWIO capability to use > /dev/mem or /dev/kmem. You can drop all other capabilities
Huh? Why would you require a capability when normal filesystem permissions already work? I mean there used to be a whole lot of ioctls and stuff that required "root", but now require a capability. Good.
So far the capabilities have always been "compatible", people who don't care needn't care.
Ok, giving someone write access to /dev/mem effectively gives away root access, but suppose we have a setuid-kmem(*) application that does something specific with kmem. We don't want it to have filesystem permissions associated with "root", so we make it setuid-kmem, and give that user access to /dev/mem.
How do I make an application set-capability-rawio?
Roger.
(*) Or setgid. Whatever.
-- ** R.E.Wolff@BitWizard.nl ** http://www.BitWizard.nl/ ** +31-15-2137555 ** *-- BitWizard writes Linux device drivers for any device you may have! --* ------ Microsoft SELLS you Windows, Linux GIVES you the whole house ------
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