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=-8.2 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, NICE_REPLY_A,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS 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 89B58C4363D for ; Fri, 25 Sep 2020 02:59:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 48DB120838 for ; Fri, 25 Sep 2020 02:59:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601002758; bh=HlyAAdYR9wyHbMonermc2egT8gBMGqZa8uXyB8IhXjU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:List-ID:From; b=DhPZSB24/aUOtj7ttwdkcqi9AE6mhy0RYUZgXJ2uYa0Ipau3ymlx6qsqUS7Afx+4g 7knti3snolfdNBzrl/OQBQ5ur0KrJ4AdKu4Y4OFMYJIj6uws4SGJZQyN7yug7xn1Er yUl7sKQbX4pjoucGzWrAxCUWfssaleqlXaTyKnVI= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726943AbgIYC7R (ORCPT ); Thu, 24 Sep 2020 22:59:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:51300 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726676AbgIYC7Q (ORCPT ); Thu, 24 Sep 2020 22:59:16 -0400 Received: from X1 (unknown [104.245.68.101]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id D4DC620838; Fri, 25 Sep 2020 02:59:14 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1601002755; bh=HlyAAdYR9wyHbMonermc2egT8gBMGqZa8uXyB8IhXjU=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=F5JoiH8AKJ04sDI6xltJ+S5/vIuoZ5y0YVdFce44I1ipKaIvaAksqmplesJ3DHsNm orqNUbtTJo2z9rY2GduEN63JeYOl4xlHV09v4dEtYTK1TyEKk02AI8jKbNd9c7/E+V m6QdEhN2hXLtO9lQ9kYvbD2v1IVCtSvvSTKvU8go= Date: Thu, 24 Sep 2020 19:59:14 -0700 From: Andrew Morton To: Rafael Aquini Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, ying.huang@intel.com Subject: Re: [PATCH] mm: swapfile: avoid split_swap_cluster() NULL pointer dereference Message-Id: <20200924195914.d240877a10e22b457bd9b45d@linux-foundation.org> In-Reply-To: <20200923134251.GN795820@optiplex-lnx> References: <20200922184838.978540-1-aquini@redhat.com> <20200922124750.67a20d9764ec098b17705407@linux-foundation.org> <20200923134251.GN795820@optiplex-lnx> X-Mailer: Sylpheed 3.5.1 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 23 Sep 2020 09:42:51 -0400 Rafael Aquini wrote: > On Tue, Sep 22, 2020 at 12:47:50PM -0700, Andrew Morton wrote: > > On Tue, 22 Sep 2020 14:48:38 -0400 Rafael Aquini wrote: > > > > > The swap area descriptor only gets struct swap_cluster_info *cluster_info > > > allocated if the swapfile is backed by non-rotational storage. > > > When the swap area is laid on top of ordinary disk spindles, lock_cluster() > > > will naturally return NULL. > > > > > > CONFIG_THP_SWAP exposes cluster_info infrastructure to a broader number of > > > use cases, and split_swap_cluster(), which is the counterpart of split_huge_page() > > > for the THPs in the swapcache, misses checking the return of lock_cluster before > > > operating on the cluster_info pointer. > > > > > > This patch addresses that issue by adding a proper check for the pointer > > > not being NULL in the wrappers cluster_{is,clear}_huge(), in order to avoid > > > crashes similar to the one below: > > > > > > ... > > > > > > Fixes: 59807685a7e77 ("mm, THP, swap: support splitting THP for THP swap out") > > > Signed-off-by: Rafael Aquini > > > > Did you consider cc:stable? > > > > UGH! I missed adding it to my cc list. Shall I just forward it, now, or > do you prefer a fresh repost? I added the cc:stable to my copy.