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=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS 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 7568BC43610 for ; Tue, 20 Nov 2018 08:06:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 46E7721104 for ; Tue, 20 Nov 2018 08:06:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 46E7721104 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726199AbeKTSd7 (ORCPT ); Tue, 20 Nov 2018 13:33:59 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45504 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725828AbeKTSdx (ORCPT ); Tue, 20 Nov 2018 13:33:53 -0500 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 8BD20308FE8F; Tue, 20 Nov 2018 08:06:05 +0000 (UTC) Received: from shodan.usersys.redhat.com (unknown [10.43.17.28]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4DF4517D6B; Tue, 20 Nov 2018 08:06:05 +0000 (UTC) Received: by shodan.usersys.redhat.com (Postfix, from userid 1000) id 831F72C1404; Tue, 20 Nov 2018 09:06:04 +0100 (CET) From: Artem Savkov To: Josh Poimboeuf Cc: Peter Zijlstra , linux-kernel@vger.kernel.org, Artem Savkov Subject: [PATCH v4 2/2] objtool: fix .cold functions parent symbols search Date: Tue, 20 Nov 2018 09:05:48 +0100 Message-Id: <20181120080548.26082-3-asavkov@redhat.com> In-Reply-To: <20181120080548.26082-1-asavkov@redhat.com> References: <20181112125519.26855-1-asavkov@redhat.com> <20181120080548.26082-1-asavkov@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Tue, 20 Nov 2018 08:06:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Because find_symbol_by_name() traverses the same lists as read_symbols() changing sym->name in place without copying it affects the result of find_symbol_by_name() and, in case when ".cold" function precedes it's parent in sec->symbol_list, can result in function being considered a parent of itself. This leads to function length being set to 0 and other consequent side-effects including a segfault in add_switch_table(). The effects of this bug are only visible when building with -ffunction-sections in KCFLAGS. Fix by copying the search string instead of modifying it in place. Fixes: 13810435b9a7 ("objtool: Support GCC 8's cold subfunctions") Signed-off-by: Artem Savkov --- tools/objtool/elf.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/tools/objtool/elf.c b/tools/objtool/elf.c index e7a7ac40e045..b8f3cca8e58b 100644 --- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -31,6 +31,8 @@ #include "elf.h" #include "warn.h" +#define MAX_NAME_LEN 128 + struct section *find_section_by_name(struct elf *elf, const char *name) { struct section *sec; @@ -298,6 +300,8 @@ static int read_symbols(struct elf *elf) /* Create parent/child links for any cold subfunctions */ list_for_each_entry(sec, &elf->sections, list) { list_for_each_entry(sym, &sec->symbol_list, list) { + char pname[MAX_NAME_LEN + 1]; + size_t pnamelen; if (sym->type != STT_FUNC) continue; sym->pfunc = sym->cfunc = sym; @@ -305,9 +309,16 @@ static int read_symbols(struct elf *elf) if (!coldstr) continue; - coldstr[0] = '\0'; - pfunc = find_symbol_by_name(elf, sym->name); - coldstr[0] = '.'; + pnamelen = coldstr - sym->name; + if (pnamelen > MAX_NAME_LEN) { + WARN("%s(): parent function name exceeds maximum length of %d characters", + sym->name, MAX_NAME_LEN); + return -1; + } + + strncpy(pname, sym->name, pnamelen); + pname[pnamelen] = '\0'; + pfunc = find_symbol_by_name(elf, pname); if (!pfunc) { WARN("%s(): can't find parent function", -- 2.19.1