linux-kernel - [PATCH 2/2] ring-buffer: Do not poll non allocated cpu buffers

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Message-Id: <20130528151749.891035971@goodmis.org>
Date:	Tue, 28 May 2013 11:15:59 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	linux-kernel@...r.kernel.org
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mauro Carvalho Chehab <mchehab@...hat.com>
Subject: [PATCH 2/2] ring-buffer: Do not poll non allocated cpu buffers

From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>

The tracing infrastructure sets up for possible CPUs, but it uses
the ring buffer polling, it is possible to call the ring buffer
polling code with a CPU that hasn't been allocated. This will cause
a kernel oops when it access a ring buffer cpu buffer that is part
of the possible cpus but hasn't been allocated yet as the CPU has never
been online.

Reported-by: Mauro Carvalho Chehab <mchehab@...hat.com>
Tested-by: Mauro Carvalho Chehab <mchehab@...hat.com>
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
 kernel/trace/ring_buffer.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b59aea2..e444ff8 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -620,6 +620,9 @@ int ring_buffer_poll_wait(struct ring_buffer *buffer, int cpu,
 	if (cpu == RING_BUFFER_ALL_CPUS)
 		work = &buffer->irq_work;
 	else {
+		if (!cpumask_test_cpu(cpu, buffer->cpumask))
+			return -EINVAL;
+
 		cpu_buffer = buffer->buffers[cpu];
 		work = &cpu_buffer->irq_work;
 	}
-- 
1.7.10.4



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