From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B58C6EB64D9 for ; Mon, 10 Jul 2023 12:26:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231608AbjGJM02 (ORCPT ); Mon, 10 Jul 2023 08:26:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33946 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229848AbjGJM0Z (ORCPT ); Mon, 10 Jul 2023 08:26:25 -0400 Received: from out30-111.freemail.mail.aliyun.com (out30-111.freemail.mail.aliyun.com [115.124.30.111]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 81BF8B1; Mon, 10 Jul 2023 05:26:22 -0700 (PDT) X-Alimail-AntiSpam: AC=PASS;BC=-1|-1;BR=01201311R161e4;CH=green;DM=||false|;DS=||;FP=0|-1|-1|-1|0|-1|-1|-1;HT=ay29a033018045176;MF=xueshuai@linux.alibaba.com;NM=1;PH=DS;RN=15;SR=0;TI=SMTPD_---0Vn44hfE_1688991975; Received: from 30.240.113.134(mailfrom:xueshuai@linux.alibaba.com fp:SMTPD_---0Vn44hfE_1688991975) by smtp.aliyun-inc.com; Mon, 10 Jul 2023 20:26:17 +0800 Message-ID: <40c4b292-e396-3a1b-f26f-ebbea93c02a8@linux.alibaba.com> Date: Mon, 10 Jul 2023 20:26:14 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [Patch v2] perf/core: Bail out early if the request AUX area is out of bound Content-Language: en-US To: Peter Zijlstra Cc: alexander.shishkin@linux.intel.com, james.clark@arm.com, leo.yan@linaro.org, mingo@redhat.com, baolin.wang@linux.alibaba.com, acme@kernel.org, mark.rutland@arm.com, jolsa@kernel.org, namhyung@kernel.org, irogers@google.com, adrian.hunter@intel.com, linux-perf-users@vger.kernel.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org References: <20230613123211.58393-1-xueshuai@linux.alibaba.com> <20230710120026.GA3034907@hirez.programming.kicks-ass.net> From: Shuai Xue In-Reply-To: <20230710120026.GA3034907@hirez.programming.kicks-ass.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/7/10 20:00, Peter Zijlstra wrote: > On Tue, Jun 13, 2023 at 08:32:11PM +0800, Shuai Xue wrote: > >> kernel/events/ring_buffer.c | 13 +++++++++++++ >> tools/perf/Documentation/perf-record.txt | 3 ++- >> 2 files changed, 15 insertions(+), 1 deletion(-) >> >> diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c >> index a0433f37b024..e514aaba9d42 100644 >> --- a/kernel/events/ring_buffer.c >> +++ b/kernel/events/ring_buffer.c >> @@ -673,6 +673,7 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event, >> bool overwrite = !(flags & RING_BUFFER_WRITABLE); >> int node = (event->cpu == -1) ? -1 : cpu_to_node(event->cpu); >> int ret = -ENOMEM, max_order; >> + size_t bytes; >> >> if (!has_aux(event)) >> return -EOPNOTSUPP; >> @@ -699,6 +700,18 @@ int rb_alloc_aux(struct perf_buffer *rb, struct perf_event *event, >> watermark = 0; >> } >> >> + /* >> + * 'rb->aux_pages' allocated by kcalloc() is a pointer array which is >> + * used to maintains AUX trace pages. The allocated page for this array >> + * is physically contiguous (and virtually contiguous) with an order of >> + * 0..MAX_ORDER. If the size of pointer array crosses the limitation set >> + * by MAX_ORDER, it reveals a WARNING. >> + * >> + * So bail out early if the request AUX area is out of bound. >> + */ >> + if (check_mul_overflow(nr_pages, sizeof(void *), &bytes) || >> + get_order(bytes) > MAX_ORDER) >> + return -EINVAL; > > This is all quite horrific :/ What's wrong with something simple: > > /* Can't allocate more than MAX_ORDER */ > if (get_order((unsigned long)nr_pages * sizeof(void*)) > MAX_ORDER) > return -EINVAL; > > If you're on 32bit then nr_pages should never be big enough to overflow, > fundamentally you'll only have 32-PAGE_SHIFT bits in nr_pages. Well, you are right. Thank you for pointing it out. I will send a new version with your simplified code :) Best Regards, Shuai > > >> rb->aux_pages = kcalloc_node(nr_pages, sizeof(void *), GFP_KERNEL, >> node); >