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=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, 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 41824C47093 for ; Tue, 1 Jun 2021 05:01:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 23AAF601FF for ; Tue, 1 Jun 2021 05:01:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232906AbhFAFDL (ORCPT ); Tue, 1 Jun 2021 01:03:11 -0400 Received: from mail.kernel.org ([198.145.29.99]:50940 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230170AbhFAFDK (ORCPT ); Tue, 1 Jun 2021 01:03:10 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 23A576102A; Tue, 1 Jun 2021 05:01:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1622523689; bh=oQlazZST/xTVF4xaTCspIjwCZZNAdsOrYEBHpFSLUMs=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=Inbx6eGf8uuOhQpwvwOY2NdQNf4FEQvyhePt97HJPaBu+P7lDcMo97U3y77wQdtLs U68yCi02NBh5197AT/2PMfcB0HNQb729i9LSwNkhfA+r/HC13kE9z/lMaA1qtbLeZA 4rcorJ3nQn69RNdpiKD0kQX8UgAydFSziuyZnbVOA/AboAZBoaw7WTHGI8VtiIPOxb oQrCUCVKWhQ/8Xt3zpwg8wQM6jw2N9kW6pXnm0FDpfb2Cwue5cRmw0EGSisGbQzVOa 204Y/snDAT2adrZeA8BUDBLl9fl1F3iDOYnf5ziuyjt5aNPL4lVdc1PxJhULJSCByz vGUSMNZnjiGjA== Date: Mon, 31 May 2021 22:01:28 -0700 From: Jakub Kicinski To: Changbin Du Cc: Alexander Viro , "David S. Miller" , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, stable@vger.kernel.org, Cong Wang , David Laight Subject: Re: [PATCH] nsfs: fix oops when ns->ops is not provided Message-ID: <20210531220128.26c0cb36@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net> In-Reply-To: <20210531153410.93150-1-changbin.du@gmail.com> References: <20210531153410.93150-1-changbin.du@gmail.com> 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 Mon, 31 May 2021 23:34:10 +0800 Changbin Du wrote: > We should not create inode for disabled namespace. A disabled namespace > sets its ns->ops to NULL. Kernel could panic if we try to create a inode > for such namespace. > > Here is an example oops in socket ioctl cmd SIOCGSKNS when NET_NS is > disabled. Kernel panicked wherever nsfs trys to access ns->ops since the > proc_ns_operations is not implemented in this case. > > [7.670023] Unable to handle kernel NULL pointer dereference at virtual address 00000010 > [7.670268] pgd = 32b54000 > [7.670544] [00000010] *pgd=00000000 > [7.671861] Internal error: Oops: 5 [#1] SMP ARM > [7.672315] Modules linked in: > [7.672918] CPU: 0 PID: 1 Comm: systemd Not tainted 5.13.0-rc3-00375-g6799d4f2da49 #16 > [7.673309] Hardware name: Generic DT based system > [7.673642] PC is at nsfs_evict+0x24/0x30 > [7.674486] LR is at clear_inode+0x20/0x9c > > So let's reject such request for disabled namespace. > > Signed-off-by: Changbin Du > Cc: > Cc: Cong Wang > Cc: Jakub Kicinski > Cc: David Laight > --- > fs/nsfs.c | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/fs/nsfs.c b/fs/nsfs.c > index 800c1d0eb0d0..6c055eb7757b 100644 > --- a/fs/nsfs.c > +++ b/fs/nsfs.c > @@ -62,6 +62,10 @@ static int __ns_get_path(struct path *path, struct ns_common *ns) > struct inode *inode; > unsigned long d; > > + /* In case the namespace is not actually enabled. */ > + if (!ns->ops) > + return -EOPNOTSUPP; > + > rcu_read_lock(); > d = atomic_long_read(&ns->stashed); > if (!d) I'm not sure why we'd pick runtime checks for something that can be perfectly easily solved at compilation time. Networking should not be asking for FDs for objects which don't exist.