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=-18.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 7549FC47082 for ; Tue, 8 Jun 2021 19:14:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F35E613AC for ; Tue, 8 Jun 2021 19:14:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S236592AbhFHTPV (ORCPT ); Tue, 8 Jun 2021 15:15:21 -0400 Received: from mail.kernel.org ([198.145.29.99]:39404 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237733AbhFHTFH (ORCPT ); Tue, 8 Jun 2021 15:05:07 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id CDB20613E1; Tue, 8 Jun 2021 18:46:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1623177972; bh=OC74NW4mCL0JZqkcszsChFoNRgnSHwYR6dc81Uur1ZQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Q967Qa7otXmnh0jKoLP+FCX5HZLKnv7DwVbmziuKH6qrUo6ZfE1iwD/hl00BlVL3F XuLKSQ04MaHp4ujX4Ycn1r0AtWE9XzAo5VBDonBWM+mF6P5e2FNAle3P9OvHwyzRq3 jZL8W9Yr5eEv4zauWTNh/uOKrEJYV0Kg661zj32A= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Li Huafei , Arnaldo Carvalho de Melo , Alexander Shishkin , "Frank Ch. Eigler" , Jianlin Lv , Jiri Olsa , Mark Rutland , Masami Hiramatsu , Namhyung Kim , Peter Zijlstra , Srikar Dronamraju , Yang Jihong , Zhang Jinhao , Sasha Levin Subject: [PATCH 5.12 029/161] perf probe: Fix NULL pointer dereference in convert_variable_location() Date: Tue, 8 Jun 2021 20:25:59 +0200 Message-Id: <20210608175946.431306540@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210608175945.476074951@linuxfoundation.org> References: <20210608175945.476074951@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Li Huafei [ Upstream commit 3cb17cce1e76ccc5499915a4d7e095a1ad6bf7ff ] If we just check whether the variable can be converted, 'tvar' should be a null pointer. However, the null pointer check is missing in the 'Constant value' execution path. The following cases can trigger this problem: $ cat test.c #include void main(void) { int a; const int b = 1; asm volatile("mov %1, %0" : "=r"(a): "i"(b)); printf("a: %d\n", a); } $ gcc test.c -o test -O -g $ sudo ./perf probe -x ./test -L "main" 0 void main(void) { 2 int a; const int b = 1; asm volatile("mov %1, %0" : "=r"(a): "i"(b)); 6 printf("a: %d\n", a); } $ sudo ./perf probe -x ./test -V "main:6" Segmentation fault The check on 'tvar' is added. If 'tavr' is a null pointer, we return 0 to indicate that the variable can be converted. Now, we can successfully show the variables that can be accessed. $ sudo ./perf probe -x ./test -V "main:6" Available variables at main:6 @ char* __fmt int a int b However, the variable 'b' cannot be tracked. $ sudo ./perf probe -x ./test -D "main:6 b" Failed to find the location of the 'b' variable at this address. Perhaps it has been optimized out. Use -V with the --range option to show 'b' location range. Error: Failed to add events. This is because __die_find_variable_cb() did not successfully match variable 'b', which has the DW_AT_const_value attribute instead of DW_AT_location. We added support for DW_AT_const_value in __die_find_variable_cb(). With this modification, we can successfully track the variable 'b'. $ sudo ./perf probe -x ./test -D "main:6 b" p:probe_test/main_L6 /home/lhf/test:0x1156 b=\1:s32 Fixes: 66f69b219716 ("perf probe: Support DW_AT_const_value constant value") Signed-off-by: Li Huafei Tested-by: Arnaldo Carvalho de Melo Cc: Alexander Shishkin Cc: Frank Ch. Eigler Cc: Jianlin Lv Cc: Jiri Olsa Cc: Mark Rutland Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Srikar Dronamraju Cc: Yang Jihong Cc: Zhang Jinhao http://lore.kernel.org/lkml/20210601092750.169601-1-lihuafei1@huawei.com Signed-off-by: Arnaldo Carvalho de Melo Signed-off-by: Sasha Levin --- tools/perf/util/dwarf-aux.c | 8 ++++++-- tools/perf/util/probe-finder.c | 3 +++ 2 files changed, 9 insertions(+), 2 deletions(-) diff --git a/tools/perf/util/dwarf-aux.c b/tools/perf/util/dwarf-aux.c index 7b2d471a6419..4343356f3cf9 100644 --- a/tools/perf/util/dwarf-aux.c +++ b/tools/perf/util/dwarf-aux.c @@ -975,9 +975,13 @@ static int __die_find_variable_cb(Dwarf_Die *die_mem, void *data) if ((tag == DW_TAG_formal_parameter || tag == DW_TAG_variable) && die_compare_name(die_mem, fvp->name) && - /* Does the DIE have location information or external instance? */ + /* + * Does the DIE have location information or const value + * or external instance? + */ (dwarf_attr(die_mem, DW_AT_external, &attr) || - dwarf_attr(die_mem, DW_AT_location, &attr))) + dwarf_attr(die_mem, DW_AT_location, &attr) || + dwarf_attr(die_mem, DW_AT_const_value, &attr))) return DIE_FIND_CB_END; if (dwarf_haspc(die_mem, fvp->addr)) return DIE_FIND_CB_CONTINUE; diff --git a/tools/perf/util/probe-finder.c b/tools/perf/util/probe-finder.c index 1b118c9c86a6..bba61b95a37a 100644 --- a/tools/perf/util/probe-finder.c +++ b/tools/perf/util/probe-finder.c @@ -190,6 +190,9 @@ static int convert_variable_location(Dwarf_Die *vr_die, Dwarf_Addr addr, immediate_value_is_supported()) { Dwarf_Sword snum; + if (!tvar) + return 0; + dwarf_formsdata(&attr, &snum); ret = asprintf(&tvar->value, "\\%ld", (long)snum); -- 2.30.2