Re: Local DoS : RedHat 6.0

[tymm () COE MISSOURI EDU (Tymm Twillman)]

-1 as a process ID argument to kill is handled by SVR4 and 4.3+BSD by
sending the signal to all processes whose real UID or saved UID is the
real or effective UID of the process sending the signal (except the signal
sender if under 4.3+BSD). So what you're actually doing is just killing
all of your processes.  You could just as well whack them all by hand.  If
you're root it'll hit about everything on the system.  (see W. Richard
Stevens "Advanced Programming in the Unix Environment" under "kill and
raise functions", p. 283-4 for more info on this).  It is standard
behavior, and not a bug.  You still can't kill others' processes.

-Tymm

On Fri, 26 May 2000, 3APA3A wrote:

> Hello ~jim,
>
> Same  results  are  under FreeBSD 3.2 with XFree86 3.3.3.1 and FreeBSD
> 4.0  with XFree86 3.3.6, so it seems to be common X(Free86 ?) problem.
> Since  X  server can be launched via telnet session it's not necessary
> to be console user to crash console this way.
>
> P.S.  no  reaction on Ctrl+Alt+Backspace or Ctrl+Alt+del, no X server,
> xdm  or  any  other  X  processes  to kill, but host is alive, you can
> startx again via telnet to solve problem.
>
>
> 24.05.00 5:45, you wrote: Local DoS : RedHat 6.0;
>
> ~> While killing yet another zombie Netscape process, I made the mistake of
> ~> typing "kill -9 -1 <pid>" as opposed to the normal "kill -9 <pid>."  For
> ~> obvious reasons, this attempted to kill every process owned by my user
> ~> and hung the entire system in the process.  (aka. I couldn't even switch
> ~> to another console to attempt recovery.)  Unfortunately the only way to
> ~> recover was to "hard boot" the system and run the risk of corrupting my
> ~> root partition in the process.  (Of course with my luck it corrupted.)
>
> ~> I actually noticed this "bug" about a year ago, but since forgot about
> ~> it.  From what I've experienced, it definitely happens when a user types
> ~> "kill -9 -1" while in RedHat 6.0's Gnome/Enlightenment or Afterstep,
> ~> however I haven't tested any other window managers or versions of Linux.
>
> /3APA3A
> http://www.security.nnov.ru