Messages in this thread Patch in this message | | | From | Vaibhav Nagarnaik <> | Subject | [PATCH] ring-buffer: Check for uninitialized cpu buffer before resizing | Date | Wed, 10 Oct 2012 16:40:27 -0700 |
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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.
Signed-off-by: Vaibhav Nagarnaik <vnagarnaik@google.com> --- kernel/trace/ring_buffer.c | 4 ++++ 1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index b32ed0e..b979426 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -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) -- 1.7.7.3
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