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=-9.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS,USER_AGENT_NEOMUTT 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 74A4EC43441 for ; Mon, 19 Nov 2018 18:02:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 461D12086A for ; Mon, 19 Nov 2018 18:02:42 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 461D12086A 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 S1731590AbeKTE1P (ORCPT ); Mon, 19 Nov 2018 23:27:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:38756 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730227AbeKTE1P (ORCPT ); Mon, 19 Nov 2018 23:27:15 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CD2B6307D853; Mon, 19 Nov 2018 18:02:40 +0000 (UTC) Received: from treble (ovpn-126-32.rdu2.redhat.com [10.10.126.32]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 4D58C60C67; Mon, 19 Nov 2018 18:02:40 +0000 (UTC) Date: Mon, 19 Nov 2018 12:02:33 -0600 From: Josh Poimboeuf To: Artem Savkov Cc: Peter Zijlstra , linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 2/2] objtool: fix .cold functions parent symbols search Message-ID: <20181119180233.mdvuah3geacujpr4@treble> References: <20181112033800.ujolxvkwzz72lxhm@treble> <20181112125519.26855-1-asavkov@redhat.com> <20181112125519.26855-3-asavkov@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20181112125519.26855-3-asavkov@redhat.com> User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.48]); Mon, 19 Nov 2018 18:02:40 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Nov 12, 2018 at 01:55:19PM +0100, Artem Savkov wrote: > 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" Same here, needs parentheses. > 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 3decd43477df..15d9acfb2c97 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); > + goto cold_err; Same here, makes more sense to just return -1 and let elf_close() clean it up I think. -- Josh