From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031149AbdDTNmz (ORCPT ); Thu, 20 Apr 2017 09:42:55 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38696 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S946061AbdDTNmy (ORCPT ); Thu, 20 Apr 2017 09:42:54 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com B20862E6066 Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx05.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=jpoimboe@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com B20862E6066 Date: Thu, 20 Apr 2017 08:42:52 -0500 From: Josh Poimboeuf To: Borislav Petkov Cc: x86-ml , lkml Subject: Re: WARNING: kernel stack regs at ffffc9000024fea8 in udevadm:92 has bad 'bp' value 00007fffc4614d30 Message-ID: <20170420134252.6dlkbbsvdotrxvzu@treble> References: <20170420110610.lkmc2a3pi3b5sgg5@pd.tnic> <20170420133021.cxf6mb4tzhjwu5el@treble> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20170420133021.cxf6mb4tzhjwu5el@treble> User-Agent: Mutt/1.6.0.1 (2016-04-01) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.29]); Thu, 20 Apr 2017 13:42:53 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Apr 20, 2017 at 08:30:21AM -0500, Josh Poimboeuf wrote: > On Thu, Apr 20, 2017 at 01:06:10PM +0200, Borislav Petkov wrote: > > Hi, > > > > the splat below started appearing on one of the boxes here with > > rc7+tip/master from yesterday. > > > > Ideas? > > Thanks for reporting it. This is another false positive. It unwinded > from an interrupt which came in right after calling into C code, but > before it could set up the frame pointer. This needs another unwinder > check. If it's recreatable, can you test with the following patch? diff --git a/arch/x86/kernel/unwind_frame.c b/arch/x86/kernel/unwind_frame.c index bda82df..abe36ff 100644 --- a/arch/x86/kernel/unwind_frame.c +++ b/arch/x86/kernel/unwind_frame.c @@ -91,16 +91,26 @@ static bool in_entry_code(unsigned long ip) return false; } +static inline unsigned long *last_frame(struct unwind_state *state) +{ + return (unsigned long *)task_pt_regs(state->task) - 2; +} + #ifdef CONFIG_X86_32 #define GCC_REALIGN_WORDS 3 #else #define GCC_REALIGN_WORDS 1 #endif +static inline unsigned long *last_aligned_frame(struct unwind_state *state) +{ + return last_frame(state) - GCC_REALIGN_WORDS; +} + static bool is_last_task_frame(struct unwind_state *state) { - unsigned long *last_bp = (unsigned long *)task_pt_regs(state->task) - 2; - unsigned long *aligned_bp = last_bp - GCC_REALIGN_WORDS; + unsigned long *last_bp = last_frame(state); + unsigned long *aligned_bp = last_aligned_frame(state); /* * We have to check for the last task frame at two different locations @@ -277,10 +287,12 @@ bool unwind_next_frame(struct unwind_state *state) /* * Don't warn if the unwinder got lost due to an interrupt in entry - * code before the stack was set up: + * code before the first frame pointer got set up: */ if (state->got_irq && in_entry_code(state->ip)) goto the_end; + if (state->regs && (unsigned long *)state->regs->sp >= last_aligned_frame(state)) + goto the_end; if (state->regs) { printk_deferred_once(KERN_WARNING