Messages in this thread | | | From | sct@dcs ... | Date | Mon, 4 Mar 96 23:00 GMT | Subject | Re: Security Hole? |
| |
Hi,
On Sun, 3 Mar 1996 16:03:43 -0500 (EST), Andrew Mileski <dmtech@magi.com> said:
> Wanted to get some EXPERT opinion on this... > I've noticed that the linux kernel allows anyone to freely > request/release IRQ, DMA, and I/O. Is this a security > hole, or am I missing something that only allows root to > do these things?
Err, I think you've missed the point. *No* user can arbitrarily request allocation of these resources --- only kernel code can. However, it is perfectly legitimate for the kernel to do so on behalf of *any* user, not just root. For example, opening /dev/fd0 will cause the kernel to reserve the floppy interface's IO space, DMA channel and IRQ line, and it is quite proper for any user to do this.
The point is that the kernel will only request allocation of IO resources if the user process has got access to the character or block device already, so the permissions in /dev/ are enforced right down to IO space automatically.
Cheers, Stephen. -- Stephen Tweedie <sct@dcs.ed.ac.uk> Department of Computer Science, Edinburgh University, Scotland.
| |