Subject: Re: [PATCH] bug in setpgid()? process groups and thread groups
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: Roland McGrath <roland@redhat.com>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>, Ulrich Drepper <drepper@redhat.com>,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>
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References: <200308021908.h72J82x10422@magilla.sf.frob.com>
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Date: 02 Aug 2003 21:51:24 +0100
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On Sad, 2003-08-02 at 20:08, Roland McGrath wrote:
> The problem exists with uids/gids as well, in the sense that they are
> changed per-thread but POSIX semantics are that setuid et al affect the
> whole process (i.e. all threads in a thread group).  I emphatically agree
> that this should be changed, and I hope we can get it done in 2.6. 

There are two reasons the uid/gid stuff can't change.

#1 Lots of non posix afflicted intelligent programmers use the per
thread uid stuff in daemons. Its really really useful

#2 Linux fundamentally assumes your security credentials don't change
mid syscall except in the specific calls we intend to.

#2 is not sanely soluble for 2.6, and of questionable value anyway, #1
is a very good reason for making libc fix up this obscure posix
stupidity itself.

Lets face it how many posix pthreads app have -performance critical
setuid/getid calls ?

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