Messages in this thread | | | Date | Wed, 24 Dec 2008 22:34:41 +0100 | From | Oleg Nesterov <> | Subject | Re: [RFC][PATCH 7/7][v4] SI_TKILL: Masquerade si_pid when crossing pid ns boundary |
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On 12/24, Sukadev Bhattiprolu wrote: > > Oleg Nesterov [oleg@redhat.com] wrote: > > | > if (p && (tgid <= 0 || task_tgid_vnr(p) == tgid)) { > | > + ns = task_active_pid_ns(p); > | > + if (ns) > | > + info.si_pid = task_tgid_nr_ns(current, ns); > | > + else > | > + info.si_pid = task_tgid_vnr(current); > | > | if ns == 0, "p" won't see the signal anyway, so all we need is > > Yes, p won't see the signal, but task_tgid_nr_ns() is not safe if ns == NULL.
Yes, I forgot that task_tgid_nr_ns() assumes ns != NULL.
> | like we do in __do_notify(). > > Yes, I had a question about ns == 0 in this patch and was wondering if I > should add a check in __do_notify() too.
I guess __do_notify() is fine, ns_of_pid() can't be NULL.
> | But. this of course doesn't work for sys_kill(). Can't we change the helpers > | which send SI_FROMUSER() signals so that they do not fill .si_pid at all? > > SI_FROMUSER() basically comes down to SI_USER and SI_TKILL (SI_QUEUE, > SI_SIGIO, SI_DETHREAD are unused ?)
Yes, I was going to kill them many times but always forget.
> SI_USER has to be masqueraded in > send_signal(). That leaves us with SI_TKILL. > > I was trying to have all si_pid settings done at origin and so the change > here for SI_TKILL. But yes, SI_USER (sys_kill() case) can't be done at > origin hence the special case for it in send_signal(). > > | Then send_signal() can do: > | > | default: > | copy_siginfo(&q->info, info); > | info.si_pid = 0; > | if (!from_ancestot_ns) > | info.si_pid = task_tgid_nr_ns(current, ...); > | > | ? > > My preference was to address SI_TKILL also at origin, but am not > particular. Yes, that will work too.
... and the code becomes more clean and simple.
I really dislike the fact that sys_kill() relies on send_signal() (this is correct), but do_tkill() and __do_notify() play with pid ns themselves. And this complicates send_signal() too.
Unless the kernel has a user which sends the "strange" SI_FROMUSER() signal without ->si_pid, of course...
Oleg.
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