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From: Steven Rostedt <rostedt@goodmis.org>
To: Miroslav Benes <mbenes@suse.cz>
Cc: linux-kernel@vger.kernel.org,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	nstange@suse.de
Subject: Re: [PATCH 1/9] ftrace: Move the recursion testing into global headers
Date: Fri, 30 Oct 2020 08:30:39 -0400	[thread overview]
Message-ID: <20201030083039.0c6135ad@oasis.local.home> (raw)
In-Reply-To: <alpine.LSU.2.21.2010301008160.22360@pobox.suse.cz>

On Fri, 30 Oct 2020 10:13:50 +0100 (CET)
Miroslav Benes <mbenes@suse.cz> wrote:

> how does this work in case of NMI? trace_get_context_bit() returns 0 (it 
> does not change later in the patch set). "start" in 
> trace_test_and_set_recursion() is 0 zero too as used later in the patch 
> set by ftrace_test_recursion_trylock(). So trace_test_and_set_recursion() 
> returns 0. That is perfectly sane, but then...
> 
> > +static __always_inline void trace_clear_recursion(int bit)
> > +{
> > +	unsigned int val = current->trace_recursion;
> > +
> > +	if (!bit)
> > +		return;  
> 
> ... the bit is not cleared here.

Yeah, I found that and fixed it yesterday, which discovered stack
overflow in perf:

  https://lore.kernel.org/r/20201030002722.766a22df@oasis.local.home

There's another bug that causes a false positive during interrupt
context transition. I have a fix for that too.

-- Steve

  reply	other threads:[~2020-10-30 12:30 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-28 11:52 [PATCH 0/9] ftrace: Have callbacks handle their own recursion Steven Rostedt
2020-10-28 11:52 ` [PATCH 1/9] ftrace: Move the recursion testing into global headers Steven Rostedt
2020-10-30  9:13   ` Miroslav Benes
2020-10-30 12:30     ` Steven Rostedt [this message]
2020-10-28 11:52 ` [PATCH 2/9] ftrace: Add ftrace_test_recursion_trylock() helper function Steven Rostedt
2020-10-28 11:52 ` [PATCH 3/9] ftrace: Optimize testing what context current is in Steven Rostedt
2020-10-28 11:52 ` [PATCH 4/9] pstore/ftrace: Add recursion protection to the ftrace callback Steven Rostedt
2020-10-28 15:59   ` Kees Cook
2020-10-28 11:52 ` [PATCH 5/9] kprobes/ftrace: " Steven Rostedt
2020-10-28 11:52   ` Steven Rostedt
2020-10-29  7:58   ` Masami Hiramatsu
2020-10-29  7:58     ` Masami Hiramatsu
2020-10-29 13:40     ` Steven Rostedt
2020-10-29 13:40       ` Steven Rostedt
2020-11-02  5:08       ` Masami Hiramatsu
2020-11-02  5:08         ` Masami Hiramatsu
2020-10-28 11:52 ` [PATCH 6/9] livepatch/ftrace: " Steven Rostedt
2020-10-29 13:51   ` Miroslav Benes
2020-10-29 14:37     ` Steven Rostedt
2020-10-30 12:28       ` Steven Rostedt
2020-10-29 14:57     ` Petr Mladek
2020-10-29 15:03       ` Miroslav Benes
2020-10-29 18:24       ` Steven Rostedt
2020-10-30  9:48         ` Miroslav Benes
2020-10-30 10:41           ` Petr Mladek
2020-10-28 11:52 ` [PATCH 7/9] perf/ftrace: " Steven Rostedt
2020-10-28 11:52 ` [PATCH 8/9] perf/ftrace: Check for rcu_is_watching() in callback function Steven Rostedt
2020-10-28 11:52 ` [PATCH 9/9] ftrace: Reverse what the RECURSION flag means in the ftrace_ops Steven Rostedt

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