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 X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D6D72C33C8C for ; Mon, 6 Jan 2020 12:03:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id B46AD207FD for ; Mon, 6 Jan 2020 12:03:44 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726080AbgAFMDn (ORCPT ); Mon, 6 Jan 2020 07:03:43 -0500 Received: from foss.arm.com ([217.140.110.172]:43360 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725821AbgAFMDn (ORCPT ); Mon, 6 Jan 2020 07:03:43 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 6ABCC328; Mon, 6 Jan 2020 04:03:42 -0800 (PST) Received: from lakrids.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 515583F534; Mon, 6 Jan 2020 04:03:41 -0800 (PST) Date: Mon, 6 Jan 2020 12:03:39 +0000 From: Mark Rutland To: Vince Weaver , Alexander Shishkin , Peter Zijlstra Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim Subject: [PATCH] perf: correctly handle failed perf_get_aux_event() (was: Re: [perf] perf_event_open() sometimes returning 0) Message-ID: <20200106120338.GC9630@lakrids.cambridge.arm.com> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Jan 02, 2020 at 02:22:47PM -0500, Vince Weaver wrote: > On Thu, 2 Jan 2020, Vince Weaver wrote: > > > so I was tracking down some odd behavior in the perf_fuzzer which turns > > out to be because perf_even_open() sometimes returns 0 (indicating a file > > descriptor of 0) even though as far as I can tell stdin is still open. Yikes. > error is triggered if aux_sample_size has non-zero value. > > seems to be this line in kernel/events/core.c: > > > if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) > goto err_locked; > > > (note, err is never set) Looks like that was introduced in commit: ab43762ef010967e ("perf: Allow normal events to output AUX data") I guess we should return -EINVAL in this case. Vince, does the below (untested) patch work for you? Thanks, Mark. ---->8---- >From c79f31b42aaf85f3a924af9218794b3bc8b79892 Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Mon, 6 Jan 2020 11:51:06 +0000 Subject: [PATCH] perf: correctly handle failed perf_get_aux_event() Vince reports a worrying issue: | so I was tracking down some odd behavior in the perf_fuzzer which turns | out to be because perf_even_open() sometimes returns 0 (indicating a file | descriptor of 0) even though as far as I can tell stdin is still open. ... and further the cause: | error is triggered if aux_sample_size has non-zero value. | | seems to be this line in kernel/events/core.c: | | if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) | goto err_locked; | | (note, err is never set) This seems to be a thinko in commit: ab43762ef010967e ("perf: Allow normal events to output AUX data") ... and we should probably return -EINVAL here, as this should only happen when the new event is mis-configured or does not have a compatible aux_event group leader. Fixes: ab43762ef010967e ("perf: Allow normal events to output AUX data") Reported-by: Vince Weaver Signed-off-by: Mark Rutland Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Alexander Shishkin --- kernel/events/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/events/core.c b/kernel/events/core.c index a1f8bde19b56..2173c23c25b4 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -11465,8 +11465,10 @@ SYSCALL_DEFINE5(perf_event_open, } } - if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) + if (perf_need_aux_event(event) && !perf_get_aux_event(event, group_leader)) { + err = -EINVAL; goto err_locked; + } /* * Must be under the same ctx::mutex as perf_install_in_context(), -- 2.11.0