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ring-buffer: Check for uninitialized cpu buffer before resizing

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With a system where, num_present_cpus < num_possible_cpus, even if all
CPUs are online, non-present CPUs don't have per_cpu buffers allocated.
If per_cpu/<cpu>/buffer_size_kb is modified for such a CPU, it can cause
a panic due to NULL dereference in ring_buffer_resize().

To fix this, resize operation is allowed only if the per-cpu buffer has
been initialized.

Link: http://lkml.kernel.org/r/1349912427-6486-1-git-send-email-vnagarnaik@google.com

Cc: stable@vger.kernel.org # 3.5+
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Vaibhav Nagarnaik 2012-10-10 16:40:27 -07:00 committed by Steven Rostedt
parent 95cf59ea72
commit 8e49f418c9
1 changed files with 4 additions and 0 deletions
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4
kernel/trace/ring_buffer.c
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@ -1567,6 +1567,10 @@ int ring_buffer_resize(struct ring_buffer *buffer, unsigned long size,
put_online_cpus();
} else {
/* Make sure this CPU has been intitialized */
if (!cpumask_test_cpu(cpu_id, buffer->cpumask))
goto out;
cpu_buffer = buffer->buffers[cpu_id];
if (nr_pages == cpu_buffer->nr_pages)