Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965849AbcKOEIH (ORCPT ); Mon, 14 Nov 2016 23:08:07 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:54619 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755263AbcKOEIF (ORCPT ); Mon, 14 Nov 2016 23:08:05 -0500 From: Wang Nan To: , CC: , , , , Wang Nan Subject: [PATCH 02/34] perf record: Fix segfault when running with suid and kptr_restrict is 1 Date: Tue, 15 Nov 2016 04:05:45 +0000 Message-ID: <20161115040617.69788-3-wangnan0@huawei.com> X-Mailer: git-send-email 2.10.1 In-Reply-To: <20161115040617.69788-1-wangnan0@huawei.com> References: <20161115040617.69788-1-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1507 Lines: 51 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 | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/util/symbol.c b/tools/perf/util/symbol.c index aecff69..420ada9 100644 --- a/tools/perf/util/symbol.c +++ b/tools/perf/util/symbol.c @@ -1962,7 +1962,7 @@ static bool symbol__read_kptr_restrict(void) char line[8]; if (fgets(line, sizeof(line), fp) != NULL) - value = (geteuid() != 0) ? + value = ((geteuid() != 0) || (getuid() != 0)) ? (atoi(line) != 0) : (atoi(line) == 2); -- 2.10.1