Date: Wed, 21 Oct 1998 16:19:28 +0300 (EET DST) From: "Jukka A. Ukkonen" <jau@jau.tmt.tele.fi> To: hackers@FreeBSD.ORG Subject: question about getsid() Message-ID: <199810211319.QAA15509@jau.tmt.tele.fi>
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Howdy, everybody!
When looking at the 3.0 getsid() code in kern_prot.c I became
a little hesitant about whether the following code will always
work...
int
getsid(p, uap)
struct proc *p;
struct getsid_args *uap;
{
if (uap->pid == 0)
goto found;
if ((p == pfind(uap->pid)) == 0)
return ESRCH;
found:
p->p_retval[0] = p->p_pgrp->pg_session->s_leader->p_pid;
return 0;
}
What will happen if the process leader has already died?
Will the original session leader's process struct still be
around available for reference or will the code fail?
My own implementation of the same thing added a new field
`s_sid' to the session struct, because I suspected problems
doing it the way the current 3.0 code does.
This new field is in my version initialized during setsid()
using the PID of the session leader, but the code does not
assume the process struct for the session leader being
available later, because `s_sid' content will be returned
by getsid().
Maybe my version has been playing extra safe in vain, but at
least that way there is no way to make the kernel panic just
by calling getsid(). Now I would like to know whether it had
been quite as safe to write my own version the way it is now
done in 3.0 or is 3.0 relying on something which is not really
guaranteed. Any comments?
Cheers,
// jau
.--- ..- -.- -.- .- .- .-.-.- ..- -.- -.- --- -. . -.
/ Jukka A. Ukkonen, Internet Services R&D / Sonera Ltd.
/__ M.Sc. (sw-eng & cs) (Phone) +358-2040-4025
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