From: Vaibhav Nagarnaik Date: Wed, 10 Oct 2012 23:40:27 +0000 (-0700) Subject: ring-buffer: Check for uninitialized cpu buffer before resizing X-Git-Tag: v3.6.4~73 X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c46d0da8fad7ef10a6f86ebd698fba26e7cadcf5;p=thirdparty%2Fkernel%2Fstable.git ring-buffer: Check for uninitialized cpu buffer before resizing commit 8e49f418c9632790bf456634742d34d97120a784 upstream. 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//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 Signed-off-by: Vaibhav Nagarnaik Signed-off-by: Steven Rostedt Signed-off-by: Greg Kroah-Hartman --- diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 49491fa7daa2d..ebd284f63e1be 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)