From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754926Ab2LLSoe (ORCPT ); Wed, 12 Dec 2012 13:44:34 -0500 Received: from hrndva-omtalb.mail.rr.com ([71.74.56.122]:30351 "EHLO hrndva-omtalb.mail.rr.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754052Ab2LLSoc (ORCPT ); Wed, 12 Dec 2012 13:44:32 -0500 X-Authority-Analysis: v=2.0 cv=JuRzXbEC c=1 sm=0 a=rXTBtCOcEpjy1lPqhTCpEQ==:17 a=mNMOxpOpBa8A:10 a=CzdeYTRZPqoA:10 a=5SG0PmZfjMsA:10 a=Q9fys5e9bTEA:10 a=meVymXHHAAAA:8 a=kgPz-38iio4A:10 a=VwQbUJbxAAAA:8 a=qvmrgIgGuK3iWGooozEA:9 a=PUjeQqilurYA:10 a=jeBq3FmKZ4MA:10 a=rXTBtCOcEpjy1lPqhTCpEQ==:117 X-Cloudmark-Score: 0 X-Authenticated-User: X-Originating-IP: 74.67.115.198 Message-ID: <1355337871.17101.340.camel@gandalf.local.home> Subject: [v3.2-v3.4 stable version][PATCH 1/2] ring-buffer: Fix NULL pointer if rb_set_head_page() fails From: Steven Rostedt To: Greg Kroah-Hartman Cc: LKML , stable Date: Wed, 12 Dec 2012 13:44:31 -0500 Content-Type: text/plain; charset="ISO-8859-15" X-Mailer: Evolution 3.4.4-1 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The function rb_set_head_page() searches the list of ring buffer pages for a the page that has the HEAD page flag set. If it does not find it, it will do a WARN_ON(), disable the ring buffer and return NULL, as this should never happen. But if this bug happens to happen, not all callers of this function can handle a NULL pointer being returned from it. That needs to be fixed. Cc: stable@vger.kernel.org # 3.0+ Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 9 +++++++-- 1 files changed, 7 insertions(+), 2 deletions(-) Index: linux-test.git/kernel/trace/ring_buffer.c =================================================================== --- linux-test.git.orig/kernel/trace/ring_buffer.c +++ linux-test.git/kernel/trace/ring_buffer.c @@ -2683,7 +2683,7 @@ unsigned long ring_buffer_oldest_event_t unsigned long flags; struct ring_buffer_per_cpu *cpu_buffer; struct buffer_page *bpage; - unsigned long ret; + unsigned long ret = 0; if (!cpumask_test_cpu(cpu, buffer->cpumask)) return 0; @@ -2698,7 +2698,8 @@ unsigned long ring_buffer_oldest_event_t bpage = cpu_buffer->reader_page; else bpage = rb_set_head_page(cpu_buffer); - ret = bpage->page->time_stamp; + if (bpage) + ret = bpage->page->time_stamp; raw_spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags); return ret; @@ -3005,6 +3006,8 @@ rb_get_reader_page(struct ring_buffer_pe * Splice the empty reader page into the list around the head. */ reader = rb_set_head_page(cpu_buffer); + if (!reader) + goto out; cpu_buffer->reader_page->list.next = rb_list_head(reader->list.next); cpu_buffer->reader_page->list.prev = reader->list.prev;