OSEC

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Re: ee using 99% cpu after user ssh session terminates abnormaly

From: Giorgos Keramidas (keramidafreebsd.org)
Date: Wed Sep 07 2005 - 18:51:32 CDT

On 2005-09-08 00:02, Craig Edwards <brainwinbot.co.uk> wrote:
> At least this is what i suspect happens. Lazy programming somewhere...
> Brooks Davis wrote:
> >On Thu, Sep 08, 2005 at 08:27:13AM +1000, talonz wrote:
> >>Recently i have been using a dialup 56k account to access the net
> >>and have noticed that when my ssh session times out and I am editing
> >>a file in ` ee ' the system goes to 99% cpu usage and stays like
> >>this till the pid is killed. This is a standard user account (not
> >>root/su)
> >>
> >>Would a user be able to create a denial of service condition on the
> >>remote system using this bug?
> >
> >No more then they could with the ablity to run any other program that
> >loops.
>
> I can duplicate this with nano on freebsd 5.4 and 5.2.1
>
> It seems that the process ignores the HUP signal maybe or ignores the
> EOF condition on stdin, and the select loop, or whatever it uses, just
> loops infinitely with nothing to read, constantly returning an error
> condition.

FWIW, pico seems to handle HUP just fine. So whatever causes nano to
enter a loop is something that is done differently in nano.

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