From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755320AbeDTOdU (ORCPT ); Fri, 20 Apr 2018 10:33:20 -0400 Received: from mail.kernel.org ([198.145.29.99]:44716 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754968AbeDTOdQ (ORCPT ); Fri, 20 Apr 2018 10:33:16 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 349842183B Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=acme@kernel.org From: Arnaldo Carvalho de Melo To: Ingo Molnar Cc: Clark Williams , linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Jiri Olsa , Alexander Shishkin , Andi Kleen , "H . Peter Anvin" , Namhyung Kim , Peter Zijlstra , Thomas Gleixner , syzkaller-bugs@googlegroups.com, x86@kernel.org, Arnaldo Carvalho de Melo Subject: [PATCH 07/17] perf: Fix sample_max_stack maximum check Date: Fri, 20 Apr 2018 11:32:17 -0300 Message-Id: <20180420143227.16030-8-acme@kernel.org> X-Mailer: git-send-email 2.14.3 In-Reply-To: <20180420143227.16030-1-acme@kernel.org> References: <20180420143227.16030-1-acme@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jiri Olsa The syzbot hit KASAN bug in perf_callchain_store having the entry stored behind the allocated bounds [1]. We miss the sample_max_stack check for the initial event that allocates callchain buffers. This missing check allows to create an event with sample_max_stack value bigger than the global sysctl maximum: # sysctl -a | grep perf_event_max_stack kernel.perf_event_max_stack = 127 # perf record -vv -C 1 -e cycles/max-stack=256/ kill ... perf_event_attr: size 112 ... sample_max_stack 256 ------------------------------------------------------------ sys_perf_event_open: pid -1 cpu 1 group_fd -1 flags 0x8 = 4 Note the '-C 1', which forces perf record to create just single event. Otherwise it opens event for every cpu, then the sample_max_stack check fails on the second event and all's fine. The fix is to run the sample_max_stack check also for the first event with callchains. [1] https://marc.info/?l=linux-kernel&m=152352732920874&w=2 Reported-by: syzbot+7c449856228b63ac951e@syzkaller.appspotmail.com Signed-off-by: Jiri Olsa Cc: Alexander Shishkin Cc: Andi Kleen Cc: H. Peter Anvin Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: syzkaller-bugs@googlegroups.com Cc: x86@kernel.org Fixes: 97c79a38cd45 ("perf core: Per event callchain limit") Link: http://lkml.kernel.org/r/20180415092352.12403-2-jolsa@kernel.org Signed-off-by: Arnaldo Carvalho de Melo --- kernel/events/callchain.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-) diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c index 772a43fea825..73cc26e321de 100644 --- a/kernel/events/callchain.c +++ b/kernel/events/callchain.c @@ -119,19 +119,22 @@ int get_callchain_buffers(int event_max_stack) goto exit; } + /* + * If requesting per event more than the global cap, + * return a different error to help userspace figure + * this out. + * + * And also do it here so that we have &callchain_mutex held. + */ + if (event_max_stack > sysctl_perf_event_max_stack) { + err = -EOVERFLOW; + goto exit; + } + if (count > 1) { /* If the allocation failed, give up */ if (!callchain_cpus_entries) err = -ENOMEM; - /* - * If requesting per event more than the global cap, - * return a different error to help userspace figure - * this out. - * - * And also do it here so that we have &callchain_mutex held. - */ - if (event_max_stack > sysctl_perf_event_max_stack) - err = -EOVERFLOW; goto exit; } -- 2.14.3