From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755887Ab1ELPYj (ORCPT ); Thu, 12 May 2011 11:24:39 -0400 Received: from cantor2.suse.de ([195.135.220.15]:45218 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753225Ab1ELPYi (ORCPT ); Thu, 12 May 2011 11:24:38 -0400 Date: Thu, 12 May 2011 17:24:37 +0200 From: Michal Marek To: Xiaochen Wang Cc: Jean Sacren , linux-kernel@vger.kernel.org Subject: Re: [PATCH] scripts/kallsyms.c: fix potential segfault Message-ID: <20110512152437.GL13293@sepie.suse.cz> References: <20110501034141.GA13473@chii> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110501034141.GA13473@chii> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 01, 2011 at 11:41:41AM +0800, Xiaochen Wang wrote: > Description: > This bug hardly appears during real kernel compiling, > because the vmlinux symbols table is huge. > > But we can still catch it under strict condition , as follows. > $ echo "c101b97b T do_fork" | ./scripts/kallsyms --all-symbols > #include > ...... > ...... > .globl kallsyms_token_table > ALGN > kallsyms_token_table: > Segmentation fault (core dumped) > $ > > If symbols table is small, all entries in token_profit[0x10000] may > decrease to 0 after several calls of compress_symbols() in optimize_result(). > In that case, find_best_token() always return 0 and > best_table[i] is set to "\0\0" and best_table_len[i] is set to 2. > > As a result, expand_symbol(best_table[0]="\0\0", best_table_len[0]=2, buf) > in write_src() will run in infinite recursion until stack overflows, > causing segfault. > > This patch checks the find_best_token() return value. If all entries in > token_profit[0x10000] become 0 according to return value, it breaks the loop > in optimize_result(). > And expand_symbol() works well when best_table_len[i] is 0. > > > Signed-off-by: Xiaochen Wang > --- > scripts/kallsyms.c | 2 ++ > 1 files changed, 2 insertions(+), 0 deletions(-) Pushed to kbuild-2.6.git#kbuild, thanks. Michal