From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757523Ab2JJXkd (ORCPT ); Wed, 10 Oct 2012 19:40:33 -0400 Received: from mail-gg0-f202.google.com ([209.85.161.202]:47162 "EHLO mail-gg0-f202.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757470Ab2JJXkb (ORCPT ); Wed, 10 Oct 2012 19:40:31 -0400 From: Vaibhav Nagarnaik To: Steven Rostedt Cc: linux-kernel@vger.kernel.org, Vaibhav Nagarnaik Subject: [PATCH] ring-buffer: Check for uninitialized cpu buffer before resizing Date: Wed, 10 Oct 2012 16:40:27 -0700 Message-Id: <1349912427-6486-1-git-send-email-vnagarnaik@google.com> X-Mailer: git-send-email 1.7.7.3 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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. Signed-off-by: Vaibhav Nagarnaik --- 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