Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750800AbdLZHVz (ORCPT ); Tue, 26 Dec 2017 02:21:55 -0500 Received: from sci-ig2.spreadtrum.com ([222.66.158.135]:17242 "EHLO SHSQR01.spreadtrum.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750705AbdLZHVy (ORCPT ); Tue, 26 Dec 2017 02:21:54 -0500 From: Chunyan Zhang To: Steven Rostedt , Ingo Molnar CC: , Jing Xia , Orson Zhai , Chunyan Zhang Subject: [PATCH] tracing: Fix crash when it fails to alloc ring buffer Date: Tue, 26 Dec 2017 15:12:53 +0800 Message-ID: <20171226071253.8968-1-chunyan.zhang@spreadtrum.com> X-Mailer: git-send-email 2.12.2 MIME-Version: 1.0 Content-Type: text/plain X-MAIL: SHSQR01.spreadtrum.com vBQ7JhWs016146 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1760 Lines: 50 From: Jing Xia Double free of the ring buffer happens when it fails to alloc new ring buffer instance for max_buffer if TRACER_MAX_TRACE is configured. The root cause is that the pointer is not set to NULL after the buffer is freed in allocate_trace_buffers(), and the freeing of the ring buffer is invoked again later if the pointer is not equal to Null, as: instance_mkdir() |-allocate_trace_buffers() |-allocate_trace_buffer(tr, &tr->trace_buffer...) |-allocate_trace_buffer(tr, &tr->max_buffer...) // allocate fail(-ENOMEM),first free // and the buffer pointer is not set to null |-ring_buffer_free(tr->trace_buffer.buffer) // out_free_tr |-free_trace_buffers() |-free_trace_buffer(&tr->trace_buffer); //if trace_buffer is not null, free again |-ring_buffer_free(buf->buffer) |-rb_free_cpu_buffer(buffer->buffers[cpu]) // ring_buffer_per_cpu is null, and // crash in ring_buffer_per_cpu->pages Signed-off-by: Jing Xia Signed-off-by: Chunyan Zhang --- kernel/trace/trace.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 73e67b6..ed1c0d1 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -7622,7 +7622,9 @@ static int allocate_trace_buffers(struct trace_array *tr, int size) allocate_snapshot ? size : 1); if (WARN_ON(ret)) { ring_buffer_free(tr->trace_buffer.buffer); + tr->trace_buffer.buffer = NULL; free_percpu(tr->trace_buffer.data); + tr->trace_buffer.data = NULL; return -ENOMEM; } tr->allocated_snapshot = allocate_snapshot; -- 2.7.4