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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,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 856B8C47092 for ; Tue, 1 Jun 2021 08:07:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 662E8613A9 for ; Tue, 1 Jun 2021 08:07:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233360AbhFAIIm (ORCPT ); Tue, 1 Jun 2021 04:08:42 -0400 Received: from mail.kernel.org ([198.145.29.99]:44992 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233162AbhFAIIl (ORCPT ); Tue, 1 Jun 2021 04:08:41 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9ECF86136E; Tue, 1 Jun 2021 08:06:57 +0000 (UTC) Date: Tue, 1 Jun 2021 10:06:54 +0200 From: Christian Brauner To: Jakub Kicinski Cc: Changbin Du , 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: <20210601080654.cl7caplm7rsagl6u@wittgenstein> References: <20210531153410.93150-1-changbin.du@gmail.com> <20210531220128.26c0cb36@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20210531220128.26c0cb36@kicinski-fedora-PC1C0HJN.hsd1.ca.comcast.net> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 31, 2021 at 10:01:28PM -0700, Jakub Kicinski wrote: > 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. Agreed! This should be fixable by sm like: diff --git a/net/socket.c b/net/socket.c index 27e3e7d53f8e..2484466d96ad 100644 --- a/net/socket.c +++ b/net/socket.c @@ -1150,10 +1150,12 @@ static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg) break; case SIOCGSKNS: err = -EPERM; +#ifdef CONFIG_NET_NS if (!ns_capable(net->user_ns, CAP_NET_ADMIN)) break; err = open_related_ns(&net->ns, get_net_ns); +#endif break; case SIOCGSTAMP_OLD: case SIOCGSTAMPNS_OLD: