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=-3.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE, SPF_PASS autolearn=no 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 3C4B7C54FCB for ; Mon, 27 Apr 2020 14:22:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 17360206BF for ; Mon, 27 Apr 2020 14:22:14 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="XXmn7huD" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727889AbgD0OWM (ORCPT ); Mon, 27 Apr 2020 10:22:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727077AbgD0OWL (ORCPT ); Mon, 27 Apr 2020 10:22:11 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:e::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AF1FC0610D5 for ; Mon, 27 Apr 2020 07:22:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=9epgz8WRXrtU6IImjK3/yyqjBcvbZymElclLrOdmIdg=; b=XXmn7huD7Rh4YffwB3SLpcq9uU Kd9pEAPv6vP/moOu88+xkOQNtVPl/yNclBs92i1ITmnqs2tWVoOVzDHCDjbWCA9ZV9eUoXbrgN5H3 7lLqydjkrMJF8Nfub7YCRG5PiNp8xwfrpD0FglnHlaM3yZwMpIJbQT/mWSUXY5xMOP5D7fgYzypk3 G7KL51QzTRRtaRrB8ahw5kB324ermwwpHaFKidd2kRhJH/M/jJK/QiZkmz/Waqct1IQ0jB/fPeAU3 H8ZtvT3AhdLjfbgszf6l0PrOVMx5So4YZLNbAGN0gHh/UGHbKats092L2gnc5X3han8SkhlWPCZe9 WLCjlTuQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1jT4e4-0002bG-F0; Mon, 27 Apr 2020 14:22:04 +0000 Date: Mon, 27 Apr 2020 07:22:04 -0700 From: Matthew Wilcox To: Waiman Long Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Kees Cook , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Changbin Du Subject: Re: [PATCH v2] mm/slub: Fix incorrect interpretation of s->offset Message-ID: <20200427142204.GG29705@bombadil.infradead.org> References: <20200427140822.18619-1-longman@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200427140822.18619-1-longman@redhat.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Apr 27, 2020 at 10:08:22AM -0400, Waiman Long wrote: > In a couple of places in the slub memory allocator, the code uses > "s->offset" as a check to see if the free pointer is put right after the > object. That check is no longer true with commit 3202fa62fb43 ("slub: > relocate freelist pointer to middle of object"). > > As a result, echoing "1" into the validate sysfs file, e.g. of dentry, > may cause a bunch of "Freepointer corrupt" error reports like the > following to appear with the system in panic afterwards. > > [ 38.579769] ============================================================================= > [ 38.580845] BUG dentry(666:pmcd.service) (Tainted: G B): Freepointer corrupt > [ 38.581948] ----------------------------------------------------------------------------- > > To fix it, use the check "s->offset == s->inuse" in the new helper > function freeptr_after_object() instead. Also add another helper function > get_info_end() to return the end of info block (inuse + free pointer > if not overlapping with object). > > Fixes: 3202fa62fb43 ("slub: relocate freelist pointer to middle of object") > Signed-off-by: Waiman Long Reviewed-by: Matthew Wilcox (Oracle)