From patchwork Tue Apr 26 02:28:54 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wang Nan X-Patchwork-Id: 66657 Delivered-To: patch@linaro.org Received: by 10.140.93.198 with SMTP id d64csp1362333qge; Mon, 25 Apr 2016 19:31:50 -0700 (PDT) X-Received: by 10.67.22.129 with SMTP id hs1mr68150pad.105.1461637909538; Mon, 25 Apr 2016 19:31:49 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id o86si1542573pfi.217.2016.04.25.19.31.49; Mon, 25 Apr 2016 19:31:49 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752121AbcDZCbg (ORCPT + 29 others); Mon, 25 Apr 2016 22:31:36 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:38664 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750843AbcDZCbX (ORCPT ); Mon, 25 Apr 2016 22:31:23 -0400 Received: from 172.24.1.47 (EHLO SZXEML424-HUB.china.huawei.com) ([172.24.1.47]) by szxrg02-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id DFZ10576; Tue, 26 Apr 2016 10:29:40 +0800 (CST) Received: from linux-4hy3.site (10.107.193.248) by SZXEML424-HUB.china.huawei.com (10.82.67.153) with Microsoft SMTP Server id 14.3.235.1; Tue, 26 Apr 2016 10:29:02 +0800 From: Wang Nan To: CC: , Wang Nan , "Arnaldo Carvalho de Melo" , Peter Zijlstra , Zefan Li , Subject: [PATCH 1/5] perf tools: Enforce ring buffer reading Date: Tue, 26 Apr 2016 02:28:54 +0000 Message-ID: <1461637738-62722-2-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1461637738-62722-1-git-send-email-wangnan0@huawei.com> References: <1461637738-62722-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020205.571ED295.006A, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 52222e3963d112c628ec77a530e2de21 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Don't read broken data after 'head' pointer. Following commits will feed perf_evlist__mmap_read() with some 'head' pointers not maintained by kernel. If 'head' pointer breaks an event, we should avoid reading from the broken event. This can happen in backward ring buffer. For example: old head | | V V +---+------+----------+----+-----+--+ |..E|D....D|C........C|B..B|A....|E.| +---+------+----------+----+-----+--+ 'old' pointer points to the beginning of 'A' and trying read from it, but 'A' has been overwritten. In this case, don't try to read from 'A', simply return NULL. Signed-off-by: Wang Nan Cc: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com --- tools/perf/util/evlist.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) -- 1.8.3.4 diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 6fb5725..85271e5 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -684,6 +684,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) struct perf_mmap *md = &evlist->mmap[idx]; u64 head; u64 old = md->prev; + int diff; unsigned char *data = md->base + page_size; union perf_event *event = NULL; @@ -694,6 +695,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) return NULL; head = perf_mmap__read_head(md); + diff = head - old; if (evlist->overwrite) { /* * If we're further behind than half the buffer, there's a chance @@ -703,7 +705,6 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) * * In either case, truncate and restart at head. */ - int diff = head - old; if (diff > md->mask / 2 || diff < 0) { fprintf(stderr, "WARNING: failed to keep up with mmap data.\n"); @@ -711,15 +712,21 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) * head points to a known good entry, start there. */ old = head; + diff = 0; } } - if (old != head) { + if (diff >= (int)sizeof(event->header)) { size_t size; event = (union perf_event *)&data[old & md->mask]; size = event->header.size; + if (size < sizeof(event->header) || diff < (int)size) { + event = NULL; + goto broken_event; + } + /* * Event straddles the mmap boundary -- header should always * be inside due to u64 alignment of output. @@ -743,6 +750,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) old += size; } +broken_event: md->prev = old; return event;