ring-buffer: Do not poll non allocated cpu buffers

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@redhat.com>
Tested-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index b59aea2c48c287f5de894efcba7d53c02fd6f279..e444ff88f0a425a00a4921291b46678b6a7efe21 100644 (file)
--- 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;
        }