From patchwork Wed Sep 21 03:48:20 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wang Nan X-Patchwork-Id: 76660 Delivered-To: patch@linaro.org Received: by 10.140.106.72 with SMTP id d66csp1820017qgf; Tue, 20 Sep 2016 20:49:20 -0700 (PDT) X-Received: by 10.98.152.138 with SMTP id d10mr46689822pfk.8.1474429759961; Tue, 20 Sep 2016 20:49:19 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id k16si33154475pfa.274.2016.09.20.20.49.19; Tue, 20 Sep 2016 20:49:19 -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 S1754728AbcIUDtR (ORCPT + 27 others); Tue, 20 Sep 2016 23:49:17 -0400 Received: from szxga01-in.huawei.com ([58.251.152.64]:38998 "EHLO szxga01-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753010AbcIUDtP (ORCPT ); Tue, 20 Sep 2016 23:49:15 -0400 Received: from 172.24.1.136 (EHLO SZXEML429-HUB.china.huawei.com) ([172.24.1.136]) by szxrg01-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id DRH60051; Wed, 21 Sep 2016 11:48:38 +0800 (CST) Received: from linux-4hy3.site (10.107.193.248) by SZXEML429-HUB.china.huawei.com (10.82.67.184) with Microsoft SMTP Server id 14.3.235.1; Wed, 21 Sep 2016 11:48:27 +0800 From: Wang Nan To: CC: , , , Wang Nan , Arnaldo Carvalho de Melo Subject: [PATCH] perf record: Fix segfault when running with suid and kptr_restrict is 1 Date: Wed, 21 Sep 2016 03:48:20 +0000 Message-ID: <1474429700-130812-1-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 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=0001.0A020204.57E20319.019C, 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: 5cd82e4a157b3e2264649dc24b8a1e33 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Before this patch perf panic if kptr_restrict set to 1 and perf is owned by root with suid set: $ whoami wangnan $ ls -l ./perf -rwsr-xr-x 1 root root 19781908 Sep 21 19:29 /home/wangnan/perf $ cat /proc/sys/kernel/kptr_restrict 1 $ cat /proc/sys/kernel/perf_event_paranoid -1 $ ./perf record -a Segmentation fault (core dumped) The reason is perf assumes it is allowed to read kptr from /proc/kallsyms when euid is root, but in fact kernel doesn't allow it reading kptr when euid and uid are not match with each other: $ cp /bin/cat . $ sudo chown root:root ./cat $ sudo chmod u+s ./cat $ cat /proc/kallsyms | grep do_fork 0000000000000000 T _do_fork <--- kptr is hidden even euid is root $ sudo cat /proc/kallsyms | grep do_fork ffffffff81080230 T _do_fork See lib/vsprintf.c for kernel side code. This patch fixes this problem by checking both uid and euid. Signed-off-by: Wang Nan Cc: Arnaldo Carvalho de Melo --- tools/perf/util/symbol.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) -- 1.8.3.4 diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index 19c9c55..9528702 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -1946,8 +1946,9 @@ static bool symbol__read_kptr_restrict(void) if (fp != NULL) { char line[8]; + if (fgets(line, sizeof(line), fp) != NULL) - value = (geteuid() != 0) ? + value = ((geteuid() != 0) || (getuid() != 0)) ? (atoi(line) != 0) : (atoi(line) == 2);