Re: SCO: "thread creation is about a thousand times faster than on

From: yodaiken@fsmlabs.com
Date: Sun Aug 27 2000 - 20:09:45 EST


On Sun, Aug 27, 2000 at 05:25:07PM -0700, Linus Torvalds wrote:
> In article <20000827051241.A24890@hq.fsmlabs.com>,
> <yodaiken@fsmlabs.com> wrote:
> >
> >POSIX says nothing, as far as I can tell, about the effect of exec on
> >threads. However, it does say pending signals must be inherited. It's
> >unclear what should happen in Linux, but it might be good for the new
> >process to still be a thread in the thread group -- although it won't
> >be sharing memory anymore.
>
> No. Simply for security purposes we _definitely_ need to "de-thread" the
> process when it does an exec. Otherwise we have "interesting" issues
> with suid execs that are part of a non-suid thread group.

I came to the same conclusion, but ..

> Note that for _pthreads_ this kind of exec is illegal anyway. Silly
> POSIX threads standard had to take user-level threading models into
> account, so under POSIX threads an execve() needs to kill off all other
> threads.

Does it? I looked in the spec, but didn't see it. That's stupid -- and
note similarly that it is easy for Linux fork to conform to POSIX spec that
the forked (new) process has no threads.

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