linux-kernel - Re: [PATCH] change kernel threads to ignore signals instead of blocking them

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] [day] [month] [year] [list]

Message-Id: <20070423194527.ab86799f.akpm@linux-foundation.org>
Date:	Mon, 23 Apr 2007 19:45:27 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Ingo Molnar <mingo@...e.hu>,
	Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] change kernel threads to ignore signals instead of
 blocking them

On Fri, 13 Apr 2007 11:31:16 +0400 Oleg Nesterov <oleg@...sign.ru> wrote:

> On top of Eric's
> 
> 	kthread-dont-depend-on-work-queues-take-2.patch
> 
> Currently kernel threads use sigprocmask(SIG_BLOCK) to protect against signals.
> This doesn't prevent the signal delivery, this only blocks signal_wake_up().
> Every "killall -33 kthreadd" means a "struct siginfo" leak.
> 
> Change kthreadd_setup() to set all handlers to SIG_IGN instead of blocking them
> (make a new helper ignore_signals() for that). If the kernel thread needs some
> signal, it should use allow_signal() anyway, and in that case it should not use
> CLONE_SIGHAND.
> 
> Note that we can't change daemonize() (should die!) in the same way, because
> it can be used along with CLONE_SIGHAND. This means that allow_signal() still
> should unblock the signal to work correctly with daemonize()ed threads.
> 
> However, disallow_signal() doesn't block the signal any longer but ignores it.
> 
> NOTE: with or without this patch the kernel threads are not protected from
> handle_stop_signal(), this seems harmless, but not good.

I'm seeing 500 zombied instances of khelper (from udev startup).  It only
happens when the utrace patches are applied.  Presumably an interaction
between utrace and one of these kthread changes.

I'll drop utrace for now.  I don't think it's getting much help from being
in -mm at present and it's getting increasingly painful to keep it merged
against all the other stuff which is happening.

Roland, I'll squirt all the extra utrace patches which I have in your direction.
Please merge them or hang on to them for later on.
-
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/