linux-kernel - Re: [BUG] signal: sighand unprotected when accessed by /proc

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Message-ID: <20140603161517.7e4ca4a8@gandalf.local.home>
Date:	Tue, 3 Jun 2014 16:15:17 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Clark Williams <williams@...hat.com>,
	"Luis Claudio R. Goncalves" <lclaudio@...g.org>
Subject: Re: [BUG] signal: sighand unprotected when accessed by /proc

On Tue, 3 Jun 2014 22:09:38 +0200
Oleg Nesterov <oleg@...hat.com> wrote:


> > Now, if that lock is released and reused (I didn't trace other tasks
> > allocating these locks), it reinitializes the lock->wait_list.
> 
> How? From where? This should be done by sighand_ctor() only?

heh, the more I look at this code, the deeper in the rabbit hole I go.

OK, I didn't understand this in the first place. I see that
sighand_ctor() is only called when the entire slab is created, correct?

That means, when you allocate a new sighand, it doesn't get
re-initialized, and the sighand->lock should still be the old lock.

That makes sense. I'll need to look at this some more :-/  Maybe
there's another bug that I'm missing and I'm climbing the wrong tree.

-- Steve
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