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Re: /dev/fb* permissions, local DoS

On Sun, Nov 19, 2000 at 06:04:01AM -0900, Ethan Benson wrote:
> does anyone know why debian has /dev/fb* with 622 permissions? 
> the reason i ask is there is a pretty nasty security problem with
> this, try the following:
> cat /dev/urandom > /dev/fb0
> on my system i get a instant kernel panic (2.2.17 from ftp.kernel.org).
> since the framebuffer devices are world writable anyone with a shell
> account can crash the system, not nice. (i have a blue G3 using
> aty128fb) 
> what is broken by setting the permissions on all the framebuffer
> devices to 0600 ?
well with fbtv or fbi there's a line like this 
(fb = open("/dev/fb0",O_WRONLY,0))

in my 2.4.0-test10 i also didn't have problem with that /dev/random > /dev/fb0

cee ya

Samuele Tonon  <samu@mclink.it>
Undergraduate Student  of  Computer Science at  University of Bologna, Italy    
System administrator at Computer Science Lab's, University of Bologna, Italy  
Founder & Member of A.A.H.T.
UIN 3155609 
          	Acid -- better living through chemistry.
			       Timothy Leary

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