Fwd: [REGRESSION 6.0.x / 6.1.x] NULL dereferencing at tracing

From: postix@posteo.eu
To: rostedt@goodmis.org
Cc: linux-kernel@vger.kernel.org, regressions@lists.linux.dev, tiwai@suse.de
Subject: Fwd: [REGRESSION 6.0.x / 6.1.x] NULL dereferencing at tracing
Date: Mon, 31 Oct 2022 20:47:01 +0000	[thread overview]
Message-ID: <71829e56-a13f-0462-37a7-a4d64c16f561@posteo.de> (raw)
In-Reply-To: <e693eb6b-28d0-d091-3df3-60f2b591c0e7@posteo.de>

> Can you apply this to see if it fixes it?
>
> I'm guessing there's a path to the release of the file descriptor where
> the ring buffer isn't allocated (and this expected it to be).
>
> I'll investigate further to see if I can find that path.
>
> -- Steve
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c 
> index 199759c73519..c1c7ce4c6ddb 100644 --- 
> a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ 
> -937,6 +937,9 @@ void ring_buffer_wake_waiters(struct trace_buffer 
> *buffer, int cpu)   	struct ring_buffer_per_cpu *cpu_buffer;
>   	struct rb_irq_work *rbwork;
>   
> + if (!buffer) + return; +   	if (cpu == RING_BUFFER_ALL_CPUS) {
>   
>   		/* Wake up individual ones too. One level recursion */

Dear Steve,

I have tested your suggested patch using kernel 6.1.0-rc2, but 
unfortunately it didn't fix the issue for me.

Thank you for looking into it though!

Best Regards

--AD