linux-kernel - Re: [PATCH 1/1] tty: disassociate

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Sat, 21 Sep 2013 16:25:07 -0400
From:	Peter Hurley <peter@...leysoftware.com>
To:	Oleg Nesterov <oleg@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jiri Slaby <jslaby@...e.cz>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	codonell <codonell@...hat.com>, Eduard Benes <ebenes@...hat.com>,
	Karel Srot <ksrot@...hat.com>,
	Matt Newsome <mnewsome@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] tty: disassociate_ctty() sends the extra SIGCONT

On 09/21/2013 02:34 PM, Oleg Nesterov wrote:
> Peter, sorry for delay, I was sick.
>
> On 09/17, Peter Hurley wrote:
>>
>> On 09/15/2013 11:50 AM, Oleg Nesterov wrote:
>>
>>> Put the "!on_exit" check back to restore the old behaviour.
>>>
>>> Cc: stable@...r.kernel.org # v3.10+
>>> Signed-off-by: Oleg Nesterov <oleg@...hat.com>
>>> Reported-by: Karel Srot <ksrot@...hat.com>
>>
>> Reviewed-by: Peter Hurley <peter@...leysoftware.com>
>
> Thanks!
>
> Can I ask the question? tty_signal_session_leader() is probably fine,
> but it _looks_ buggy or at least confusing to me.
>
> 		do_each_pid_task(tty->session, PIDTYPE_SID, p) {
> 			spin_lock_irq(&p->sighand->siglock);
> 			if (p->signal->tty == tty) {
> 				p->signal->tty = NULL;
> 				/* We defer the dereferences outside fo
> 				   the tasklist lock */
> 				refs++;
> 			}
> 			if (!p->signal->leader) {
> 				spin_unlock_irq(&p->sighand->siglock);
> 				continue;
> 			}
> 			__group_send_sig_info(SIGHUP, SEND_SIG_PRIV, p);
> 			__group_send_sig_info(SIGCONT, SEND_SIG_PRIV, p);
> 			put_pid(p->signal->tty_old_pgrp);  /* A noop */
> 			spin_lock(&tty->ctrl_lock);
> 			tty_pgrp = get_pid(tty->pgrp);
>
> I guess this can happen only once, so we could even add WARN_ON(tty_pgrp)
> before get_pid(). But this look confusing, as if we can do get_pid()
> multiple times and leak tty->pgrp.
>
> 			if (tty->pgrp)
> 				p->signal->tty_old_pgrp = get_pid(tty->pgrp);
>
> else? We already did put_pid(tty_old_pgrp), we should clear it.
>
> IOW, do you think the patch below makes sense or I missed something?
> Just curious.

The code block you're referring to only executes once because there is
only one session leader.

Regards,
Peter Hurley

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/