From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934598AbXGQQEv (ORCPT ); Tue, 17 Jul 2007 12:04:51 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756159AbXGQQEn (ORCPT ); Tue, 17 Jul 2007 12:04:43 -0400 Received: from mx2.mail.elte.hu ([157.181.151.9]:46610 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756371AbXGQQEn (ORCPT ); Tue, 17 Jul 2007 12:04:43 -0400 Date: Tue, 17 Jul 2007 18:04:25 +0200 From: Ingo Molnar To: Oleg Nesterov Cc: Chuck Ebbert <76306.1226@compuserve.com>, Linus Torvalds , Roland McGrath , linux-kernel@vger.kernel.org Subject: [patch] i386: remove unnecessary code Message-ID: <20070717160425.GA26401@elte.hu> References: <20070717154638.GA342@tv-sign.ru> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20070717154638.GA342@tv-sign.ru> User-Agent: Mutt/1.5.14 (2007-02-12) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.0 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.1.7-deb -1.0 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Oleg Nesterov wrote: > I am really puzzled by set_fs(USER_DS) in setup_frame/setup_rt_frame. > > How is it possible that current->addr_limit != USER_DS ? If this _is_ > possible, how can can we trust the result of access_ok() above? hm, this is _ancient_ code (possibly dating back to the pharaohs). If we are in KERNEL_DS then we call do_signal() then we are most likely a kernel thread and regs->esp points to the kernel stack ... the result of which would be a quite spectacular crash anyway. Patch below. Ingo -----------------------------> Subject: [patch] i386: remove unnecessary code From: Ingo Molnar Oleg Nesterov pointed out that the set_fs() calls in setup_frame() and setup_rt_frame() were superfluous. Signed-off-by: Ingo Molnar --- arch/i386/kernel/signal.c | 2 -- 1 file changed, 2 deletions(-) Index: linux/arch/i386/kernel/signal.c =================================================================== --- linux.orig/arch/i386/kernel/signal.c +++ linux/arch/i386/kernel/signal.c @@ -380,7 +380,6 @@ static int setup_frame(int sig, struct k regs->edx = (unsigned long) 0; regs->ecx = (unsigned long) 0; - set_fs(USER_DS); regs->xds = __USER_DS; regs->xes = __USER_DS; regs->xss = __USER_DS; @@ -474,7 +473,6 @@ static int setup_rt_frame(int sig, struc regs->edx = (unsigned long) &frame->info; regs->ecx = (unsigned long) &frame->uc; - set_fs(USER_DS); regs->xds = __USER_DS; regs->xes = __USER_DS; regs->xss = __USER_DS;