linux-kernel - Re: [PATCH 1/1] tracing: Simplify trace_array

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Message-ID: <20130719163312.GA21544@redhat.com>
Date:	Fri, 19 Jul 2013 18:33:12 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] tracing: Simplify trace_array_get()

On 07/19, Steven Rostedt wrote:
>
> On Fri, 2013-07-19 at 17:51 +0200, Oleg Nesterov wrote:
> >  	mutex_lock(&trace_types_lock);
> > -	list_for_each_entry(tr, &ftrace_trace_arrays, list) {
> > -		if (tr == this_tr) {
> > -			tr->ref++;
> > -			ret = 0;
> > -			break;
> > -		}
> > +	if (!list_empty(&this_tr->list)) {
>
> Because this_tr can be freed outside the lock. Accessing this_tr->list
> can cause a crash.

Aaah, indeed.

Thanks Steven!

Oleg.

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