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

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Message-ID: <20140603200938.GA3384@redhat.com>
Date:	Tue, 3 Jun 2014 22:09:38 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
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>
Subject: Re: [BUG] signal: sighand unprotected when accessed by /proc

Steven, I am already sleeping, probably I just need to re-read your
email tomorrow, but...

On 06/03, Steven Rostedt wrote:
>
> When we convert the spin_lock into a rtmutex, when we hit the lock and
> it was contended (the task was in the process of exiting and it takes
> the lock to set tsk->sighand to NULL), instead of spinning, the task
> adds itself to the lock->wait_list and goes to sleep.

This is clear,

> 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?

Oleg.

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