Re: [PATCH 12/13] hrtimer: create a "timer_slack" field in the task struct

From: Ulrich Drepper
Date: Sun Sep 14 2008 - 12:04:18 EST

On Sun, Sep 14, 2008 at 8:57 AM, Pavel Machek <pavel@xxxxxxx> wrote:
>> LD_PRELOAD and other variables are ignored in security-relevant
>> contexts and environments are cleared in many situations. Sure, you
> ...but that's okay, right? You would not want passwd to inherit huge
> slack specified by attacker...?

No, it's not OK. There are enough apps which are privileged and need
to be handled this way. Take the X server, for instance.

> Well, it is not too much, but... is the cost for userspace really
> significant? You'd clearly want it stored in environment, not
> filesystem...

You cannot really use the environment for anything meaningful.
Especially for this case, you couldn't change the setting for a
running process. What a fully-userlevel implementation would have to
do is read the value from a file and monitor the file for changes for
every new poll/select call. That's a huge cost.
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