linux-kernel - Re: [PATCH -mm] proc: don't take ->siglock for /proc/pid/oom

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]

Message-ID: <alpine.DEB.2.00.1004010128050.6285@chino.kir.corp.google.com>
Date:	Thu, 1 Apr 2010 01:32:13 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Oleg Nesterov <oleg@...hat.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	anfei <anfei.zhou@...il.com>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	nishimura@....nes.nec.co.jp,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Mel Gorman <mel@....ul.ie>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH -mm] proc: don't take ->siglock for /proc/pid/oom_adj

On Thu, 1 Apr 2010, Oleg Nesterov wrote:

> > That doesn't work for depraceted_mode (sic), you'd need to test for
> > OOM_ADJUST_MIN and OOM_ADJUST_MAX in that case.
> 
> Yes, probably "if (depraceted_mode)" should do more checks, I didn't try
> to verify that MIN/MAX are correctly converted. I showed this code to explain
> what I mean.
> 

Ok, please cc me on the patch, it will be good to get rid of the duplicate 
code and remove oom_adj from struct signal_struct.

> > There have been efforts to reuse as much of this code as possible for
> > other sysctl handlers as well, you might be better off looking for
> 
> David, sorry ;) Right now I'd better try to stop the overloading of
> ->siglock. And, I'd like to shrink struct_signal if possible, but this
> is minor.
> 

Do we need ->siglock?  Why can't we just do

	struct sighand_struct *sighand;
	struct signal_struct *sig;

	rcu_read_lock();
	sighand = rcu_dereference(task->sighand);
	if (!sighand) {
		rcu_read_unlock();
		return;
	}
	sig = task->signal;

	... load/store to sig ...

	rcu_read_unlock();

instead?
--
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/