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=-8.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 63398C31E40 for ; Thu, 15 Aug 2019 09:21:34 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3455620644 for ; Thu, 15 Aug 2019 09:21:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731238AbfHOJVd (ORCPT ); Thu, 15 Aug 2019 05:21:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35534 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730212AbfHOJVc (ORCPT ); Thu, 15 Aug 2019 05:21:32 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 16A535AFE9; Thu, 15 Aug 2019 09:21:32 +0000 (UTC) Received: from [10.72.12.184] (ovpn-12-184.pek2.redhat.com [10.72.12.184]) by smtp.corp.redhat.com (Postfix) with ESMTP id 46E1F95A4F; Thu, 15 Aug 2019 09:21:29 +0000 (UTC) Subject: Re: [PATCH] tun: fix use-after-free when register netdev failed To: Yang Yingliang , netdev@vger.kernel.org Cc: xiyou.wangcong@gmail.com, davem@davemloft.net References: <1565857122-24660-1-git-send-email-yangyingliang@huawei.com> From: Jason Wang Message-ID: Date: Thu, 15 Aug 2019 17:21:27 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1565857122-24660-1-git-send-email-yangyingliang@huawei.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.39]); Thu, 15 Aug 2019 09:21:32 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2019/8/15 下午4:18, Yang Yingliang wrote: > I got a UAF repport in tun driver when doing fuzzy test: > > [ 466.269490] ================================================================== > [ 466.271792] BUG: KASAN: use-after-free in tun_chr_read_iter+0x2ca/0x2d0 > [ 466.271806] Read of size 8 at addr ffff888372139250 by task tun-test/2699 > [ 466.271810] > [ 466.271824] CPU: 1 PID: 2699 Comm: tun-test Not tainted 5.3.0-rc1-00001-g5a9433db2614-dirty #427 > [ 466.271833] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.12.1-0-ga5cab58e9a3f-prebuilt.qemu.org 04/01/2014 > [ 466.271838] Call Trace: > [ 466.271858] dump_stack+0xca/0x13e > [ 466.271871] ? tun_chr_read_iter+0x2ca/0x2d0 > [ 466.271890] print_address_description+0x79/0x440 > [ 466.271906] ? vprintk_func+0x5e/0xf0 > [ 466.271920] ? tun_chr_read_iter+0x2ca/0x2d0 > [ 466.271935] __kasan_report+0x15c/0x1df > [ 466.271958] ? tun_chr_read_iter+0x2ca/0x2d0 > [ 466.271976] kasan_report+0xe/0x20 > [ 466.271987] tun_chr_read_iter+0x2ca/0x2d0 > [ 466.272013] do_iter_readv_writev+0x4b7/0x740 > [ 466.272032] ? default_llseek+0x2d0/0x2d0 > [ 466.272072] do_iter_read+0x1c5/0x5e0 > [ 466.272110] vfs_readv+0x108/0x180 > [ 466.299007] ? compat_rw_copy_check_uvector+0x440/0x440 > [ 466.299020] ? fsnotify+0x888/0xd50 > [ 466.299040] ? __fsnotify_parent+0xd0/0x350 > [ 466.299064] ? fsnotify_first_mark+0x1e0/0x1e0 > [ 466.304548] ? vfs_write+0x264/0x510 > [ 466.304569] ? ksys_write+0x101/0x210 > [ 466.304591] ? do_preadv+0x116/0x1a0 > [ 466.304609] do_preadv+0x116/0x1a0 > [ 466.309829] do_syscall_64+0xc8/0x600 > [ 466.309849] entry_SYSCALL_64_after_hwframe+0x49/0xbe > [ 466.309861] RIP: 0033:0x4560f9 > [ 466.309875] Code: 00 00 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48 > [ 466.309889] RSP: 002b:00007ffffa5166e8 EFLAGS: 00000206 ORIG_RAX: 0000000000000127 > [ 466.322992] RAX: ffffffffffffffda RBX: 0000000000400460 RCX: 00000000004560f9 > [ 466.322999] RDX: 0000000000000003 RSI: 00000000200008c0 RDI: 0000000000000003 > [ 466.323007] RBP: 00007ffffa516700 R08: 0000000000000004 R09: 0000000000000000 > [ 466.323014] R10: 0000000000000000 R11: 0000000000000206 R12: 000000000040cb10 > [ 466.323021] R13: 0000000000000000 R14: 00000000006d7018 R15: 0000000000000000 > [ 466.323057] > [ 466.323064] Allocated by task 2605: > [ 466.335165] save_stack+0x19/0x80 > [ 466.336240] __kasan_kmalloc.constprop.8+0xa0/0xd0 > [ 466.337755] kmem_cache_alloc+0xe8/0x320 > [ 466.339050] getname_flags+0xca/0x560 > [ 466.340229] user_path_at_empty+0x2c/0x50 > [ 466.341508] vfs_statx+0xe6/0x190 > [ 466.342619] __do_sys_newstat+0x81/0x100 > [ 466.343908] do_syscall_64+0xc8/0x600 > [ 466.345303] entry_SYSCALL_64_after_hwframe+0x49/0xbe > [ 466.347034] > [ 466.347517] Freed by task 2605: > [ 466.348471] save_stack+0x19/0x80 > [ 466.349476] __kasan_slab_free+0x12e/0x180 > [ 466.350726] kmem_cache_free+0xc8/0x430 > [ 466.351874] putname+0xe2/0x120 > [ 466.352921] filename_lookup+0x257/0x3e0 > [ 466.354319] vfs_statx+0xe6/0x190 > [ 466.355498] __do_sys_newstat+0x81/0x100 > [ 466.356889] do_syscall_64+0xc8/0x600 > [ 466.358037] entry_SYSCALL_64_after_hwframe+0x49/0xbe > [ 466.359567] > [ 466.360050] The buggy address belongs to the object at ffff888372139100 > [ 466.360050] which belongs to the cache names_cache of size 4096 > [ 466.363735] The buggy address is located 336 bytes inside of > [ 466.363735] 4096-byte region [ffff888372139100, ffff88837213a100) > [ 466.367179] The buggy address belongs to the page: > [ 466.368604] page:ffffea000dc84e00 refcount:1 mapcount:0 mapping:ffff8883df1b4f00 index:0x0 compound_mapcount: 0 > [ 466.371582] flags: 0x2fffff80010200(slab|head) > [ 466.372910] raw: 002fffff80010200 dead000000000100 dead000000000122 ffff8883df1b4f00 > [ 466.375209] raw: 0000000000000000 0000000000070007 00000001ffffffff 0000000000000000 > [ 466.377778] page dumped because: kasan: bad access detected > [ 466.379730] > [ 466.380288] Memory state around the buggy address: > [ 466.381844] ffff888372139100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 466.384009] ffff888372139180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 466.386131] >ffff888372139200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 466.388257] ^ > [ 466.390234] ffff888372139280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 466.392512] ffff888372139300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb > [ 466.394667] ================================================================== > > tun_chr_read_iter() accessed the memory which freed by free_netdev() > called by tun_set_iff(): > > CPUA CPUB > tun_set_iff() > alloc_netdev_mqs() > tun_attach() > tun_chr_read_iter() > tun_get() > register_netdevice() > tun_detach_all() > synchronize_net() > tun_do_read() > tun_ring_recv() > schedule() > free_netdev() > tun_put() <-- UAF > > Set a new bit in tun->flag if register_netdevice() successed, > without this bit, tun_get() returns NULL to avoid using a > freed tun pointer. Good catch. Some comments inline. > > Fixes: eb0fb363f920 ("tuntap: attach queue 0 before registering netdevice") > Reported-by: Hulk Robot > Signed-off-by: Yang Yingliang > --- > drivers/net/tun.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index db16d7a13e00..cbd60c276c40 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -115,6 +115,7 @@ do { \ > /* High bits in flags field are unused. */ > #define TUN_VNET_LE 0x80000000 > #define TUN_VNET_BE 0x40000000 > +#define TUN_DEV_REGISTERED 0x20000000 > > #define TUN_FEATURES (IFF_NO_PI | IFF_ONE_QUEUE | IFF_VNET_HDR | \ > IFF_MULTI_QUEUE | IFF_NAPI | IFF_NAPI_FRAGS) > @@ -719,8 +720,10 @@ static void __tun_detach(struct tun_file *tfile, bool clean) > netif_carrier_off(tun->dev); > > if (!(tun->flags & IFF_PERSIST) && > - tun->dev->reg_state == NETREG_REGISTERED) > + tun->dev->reg_state == NETREG_REGISTERED) { > unregister_netdevice(tun->dev); > + tun->flags &= ~TUN_DEV_REGISTERED; > + } > } > if (tun) > xdp_rxq_info_unreg(&tfile->xdp_rxq); > @@ -884,8 +887,10 @@ static struct tun_struct *tun_get(struct tun_file *tfile) > > rcu_read_lock(); > tun = rcu_dereference(tfile->tun); > - if (tun) > + if (tun && (tun->flags & TUN_DEV_REGISTERED)) > dev_hold(tun->dev); > + else > + tun = NULL; > rcu_read_unlock(); > > return tun; > @@ -2836,6 +2841,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) > err = register_netdevice(tun->dev); > if (err < 0) > goto err_detach; > + tun->flags |= TUN_DEV_REGISTERED; > } > > netif_carrier_on(tun->dev); This looks just a duplicated of netdev->state? However it lacks sufficient synchronization like barriers or locks. How about: - call tun_set_real_num_queues() before register_netdevice() this can have the same result as what  eb0fb363f920 did. - move tun_attach() after register_netdevice() this makes sure we won't publish tfile->tun until we are sure at least one refcnt is held by register_netdevice()? Thanks