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
--
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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