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=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 AC7F0C47096 for ; Thu, 3 Jun 2021 13:15:30 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 29AA4613DE for ; Thu, 3 Jun 2021 13:15:28 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 29AA4613DE Authentication-Results: mail.kernel.org; dmarc=fail (p=quarantine dis=none) header.from=suse.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id C0D706B00B0; Thu, 3 Jun 2021 09:15:27 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id BE21A6B00B2; Thu, 3 Jun 2021 09:15:27 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A40CA6B00B0; Thu, 3 Jun 2021 09:15:27 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0134.hostedemail.com [216.40.44.134]) by kanga.kvack.org (Postfix) with ESMTP id 7111F6B00B0 for ; Thu, 3 Jun 2021 09:15:27 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 07AFB8117EE7 for ; Thu, 3 Jun 2021 13:15:27 +0000 (UTC) X-FDA: 78212459094.22.DFAFF70 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by imf21.hostedemail.com (Postfix) with ESMTP id 15E61E000274 for ; Thu, 3 Jun 2021 13:15:07 +0000 (UTC) Received: from relay2.suse.de (unknown [149.44.160.134]) by smtp-out2.suse.de (Postfix) with ESMTP id 4C46A1FD3D; Thu, 3 Jun 2021 13:15:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1622726125; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=in/G7fzdUcdCv5ZvDLh1mBytHpj8YQlTgchvITKLgrI=; b=s2HVubBUAFMVIIBjzD6M5Q/51LKPRFDNTX+TTbtibiMCt35kBNIuyO8UTr91ktRk6WvVrg YUozOtp8nzkqaAWHnmIdwXvE/+KbqCVhfJqKoVvLJ+12M5gUE/Rg/qrXlMDhnHrMQ6vOuG nUTUy6G7nHvpT3jxMX9wAubNQ0SlcCk= Received: from suse.cz (unknown [10.100.224.162]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by relay2.suse.de (Postfix) with ESMTPS id C6390A3B8B; Thu, 3 Jun 2021 13:15:24 +0000 (UTC) Date: Thu, 3 Jun 2021 15:15:24 +0200 From: Petr Mladek To: Stephen Boyd Cc: Andrew Morton , linux-kernel@vger.kernel.org, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Vlastimil Babka , linux-mm@kvack.org, Joe Perches Subject: Re: [PATCH v3 4/4] slub: Force on no_hash_pointers when slub_debug is enabled Message-ID: References: <20210601182202.3011020-1-swboyd@chromium.org> <20210601182202.3011020-5-swboyd@chromium.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210601182202.3011020-5-swboyd@chromium.org> Authentication-Results: imf21.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=s2HVubBU; spf=pass (imf21.hostedemail.com: domain of pmladek@suse.com designates 195.135.220.29 as permitted sender) smtp.mailfrom=pmladek@suse.com; dmarc=pass (policy=quarantine) header.from=suse.com X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 15E61E000274 X-Stat-Signature: pnqdtot5x1czkezi6466sf6fcz7neida X-HE-Tag: 1622726107-153984 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue 2021-06-01 11:22:02, Stephen Boyd wrote: > Obscuring the pointers that slub shows when debugging makes for some > confusing slub debug messages: > > Padding overwritten. 0x0000000079f0674a-0x000000000d4dce17 > > Those addresses are hashed for kernel security reasons. If we're trying > to be secure with slub_debug on the commandline we have some big > problems given that we dump whole chunks of kernel memory to the kernel > logs. Let's force on the no_hash_pointers commandline flag when > slub_debug is on the commandline. This makes slub debug messages more > meaningful and if by chance a kernel address is in some slub debug > object dump we will have a better chance of figuring out what went > wrong. > > Note that we don't use %px in the slub code because we want to reduce > the number of places that %px is used in the kernel. This also nicely > prints a big fat warning at kernel boot if slub_debug is on the > commandline so that we know that this kernel shouldn't be used on > production systems. > > Signed-off-by: Stephen Boyd Acked-by: Petr Mladek Best Regards, Petr