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=-6.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, 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 1CCDEC10F0E for ; Mon, 15 Apr 2019 13:23:55 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E02E420880 for ; Mon, 15 Apr 2019 13:23:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727445AbfDONXx (ORCPT ); Mon, 15 Apr 2019 09:23:53 -0400 Received: from mx1.redhat.com ([209.132.183.28]:58988 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727218AbfDONXx (ORCPT ); Mon, 15 Apr 2019 09:23:53 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 9CBAB3092648; Mon, 15 Apr 2019 13:23:47 +0000 (UTC) Received: from treble (ovpn-120-105.rdu2.redhat.com [10.10.120.105]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 9B92060150; Mon, 15 Apr 2019 13:23:43 +0000 (UTC) Date: Mon, 15 Apr 2019 08:23:39 -0500 From: Josh Poimboeuf To: Thomas Gleixner Cc: Andy Lutomirski , LKML , X86 ML , Sean Christopherson , Andrew Morton , Pekka Enberg , Linux-MM Subject: Re: [patch V4 01/32] mm/slab: Fix broken stack trace storage Message-ID: <20190415132339.wiqyzygqklliyml7@treble> References: <20190414155936.679808307@linutronix.de> <20190414160143.591255977@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20180716 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.43]); Mon, 15 Apr 2019 13:23:52 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 15, 2019 at 11:02:58AM +0200, Thomas Gleixner wrote: > kstack_end() is broken on interrupt stacks as they are not guaranteed to be > sized THREAD_SIZE and THREAD_SIZE aligned. > > Use the stack tracer instead. Remove the pointless pointer increment at the > end of the function while at it. > > Fixes: 98eb235b7feb ("[PATCH] page unmapping debug") - History tree > Signed-off-by: Thomas Gleixner > Cc: Andrew Morton > Cc: Pekka Enberg > Cc: linux-mm@kvack.org > --- > V4: Made the code simpler to understand (Andy) and make it actually compile > --- > mm/slab.c | 30 ++++++++++++++---------------- > 1 file changed, 14 insertions(+), 16 deletions(-) > > --- a/mm/slab.c > +++ b/mm/slab.c > @@ -1470,33 +1470,31 @@ static bool is_debug_pagealloc_cache(str > static void store_stackinfo(struct kmem_cache *cachep, unsigned long *addr, > unsigned long caller) > { > - int size = cachep->object_size; > + int size = cachep->object_size / sizeof(unsigned long); > > addr = (unsigned long *)&((char *)addr)[obj_offset(cachep)]; > > - if (size < 5 * sizeof(unsigned long)) > + if (size < 5) > return; > > *addr++ = 0x12345678; > *addr++ = caller; > *addr++ = smp_processor_id(); > - size -= 3 * sizeof(unsigned long); > + size -= 3; > +#ifdef CONFIG_STACKTRACE > { > - unsigned long *sptr = &caller; > - unsigned long svalue; > - > - while (!kstack_end(sptr)) { > - svalue = *sptr++; > - if (kernel_text_address(svalue)) { > - *addr++ = svalue; > - size -= sizeof(unsigned long); > - if (size <= sizeof(unsigned long)) > - break; > - } > - } > + struct stack_trace trace = { > + /* Leave one for the end marker below */ > + .max_entries = size - 1, > + .entries = addr, > + .skip = 3, > + }; > > + save_stack_trace(&trace); > + addr += trace.nr_entries; > } > - *addr++ = 0x87654321; > +#endif > + *addr = 0x87654321; Looks like stack_trace.nr_entries isn't initialized? (though this code gets eventually replaced by a later patch) Who actually reads this stack trace? I couldn't find a consumer. -- Josh