From patchwork Mon Feb 5 21:23:01 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Abeni X-Patchwork-Id: 869580 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3zb0v45qZMz9sR8 for ; Tue, 6 Feb 2018 08:23:28 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751988AbeBEVX0 (ORCPT ); Mon, 5 Feb 2018 16:23:26 -0500 Received: from mx1.redhat.com ([209.132.183.28]:52444 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbeBEVXX (ORCPT ); Mon, 5 Feb 2018 16:23:23 -0500 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 ECD037824D; Mon, 5 Feb 2018 21:23:22 +0000 (UTC) Received: from dhcppc0.redhat.com (ovpn-116-26.ams2.redhat.com [10.36.116.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6BF53609A5; Mon, 5 Feb 2018 21:23:17 +0000 (UTC) From: Paolo Abeni To: netdev@vger.kernel.org Cc: "David S. Miller" , Jamal Hadi Salim , Cong Wang , Jiri Pirko , Li Shuang , Ivan Vecera Subject: [PATCH net v4] cls_u32: fix use after free in u32_destroy_key() Date: Mon, 5 Feb 2018 22:23:01 +0100 Message-Id: <096ddb46db4fcb134ee7ccaf8de74397ef84e1ec.1517865640.git.pabeni@redhat.com> 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 [10.5.110.28]); Mon, 05 Feb 2018 21:23:23 +0000 (UTC) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Li Shuang reported an Oops with cls_u32 due to an use-after-free in u32_destroy_key(). The use-after-free can be triggered with: dev=lo tc qdisc add dev $dev root handle 1: htb default 10 tc filter add dev $dev parent 1: prio 5 handle 1: protocol ip u32 divisor 256 tc filter add dev $dev protocol ip parent 1: prio 5 u32 ht 800:: match ip dst\ 10.0.0.0/8 hashkey mask 0x0000ff00 at 16 link 1: tc qdisc del dev $dev root Which causes the following kasan splat: ================================================================== BUG: KASAN: use-after-free in u32_destroy_key.constprop.21+0x117/0x140 [cls_u32] Read of size 4 at addr ffff881b83dae618 by task kworker/u48:5/571 CPU: 17 PID: 571 Comm: kworker/u48:5 Not tainted 4.15.0+ #87 Hardware name: Dell Inc. PowerEdge R730/072T6D, BIOS 2.1.7 06/16/2016 Workqueue: tc_filter_workqueue u32_delete_key_freepf_work [cls_u32] Call Trace: dump_stack+0xd6/0x182 ? dma_virt_map_sg+0x22e/0x22e print_address_description+0x73/0x290 kasan_report+0x277/0x360 ? u32_destroy_key.constprop.21+0x117/0x140 [cls_u32] u32_destroy_key.constprop.21+0x117/0x140 [cls_u32] u32_delete_key_freepf_work+0x1c/0x30 [cls_u32] process_one_work+0xae0/0x1c80 ? sched_clock+0x5/0x10 ? pwq_dec_nr_in_flight+0x3c0/0x3c0 ? _raw_spin_unlock_irq+0x29/0x40 ? trace_hardirqs_on_caller+0x381/0x570 ? _raw_spin_unlock_irq+0x29/0x40 ? finish_task_switch+0x1e5/0x760 ? finish_task_switch+0x208/0x760 ? preempt_notifier_dec+0x20/0x20 ? __schedule+0x839/0x1ee0 ? check_noncircular+0x20/0x20 ? firmware_map_remove+0x73/0x73 ? find_held_lock+0x39/0x1c0 ? worker_thread+0x434/0x1820 ? lock_contended+0xee0/0xee0 ? lock_release+0x1100/0x1100 ? init_rescuer.part.16+0x150/0x150 ? retint_kernel+0x10/0x10 worker_thread+0x216/0x1820 ? process_one_work+0x1c80/0x1c80 ? lock_acquire+0x1a5/0x540 ? lock_downgrade+0x6b0/0x6b0 ? sched_clock+0x5/0x10 ? lock_release+0x1100/0x1100 ? compat_start_thread+0x80/0x80 ? do_raw_spin_trylock+0x190/0x190 ? _raw_spin_unlock_irq+0x29/0x40 ? trace_hardirqs_on_caller+0x381/0x570 ? _raw_spin_unlock_irq+0x29/0x40 ? finish_task_switch+0x1e5/0x760 ? finish_task_switch+0x208/0x760 ? preempt_notifier_dec+0x20/0x20 ? __schedule+0x839/0x1ee0 ? kmem_cache_alloc_trace+0x143/0x320 ? firmware_map_remove+0x73/0x73 ? sched_clock+0x5/0x10 ? sched_clock_cpu+0x18/0x170 ? find_held_lock+0x39/0x1c0 ? schedule+0xf3/0x3b0 ? lock_downgrade+0x6b0/0x6b0 ? __schedule+0x1ee0/0x1ee0 ? do_wait_intr_irq+0x340/0x340 ? do_raw_spin_trylock+0x190/0x190 ? _raw_spin_unlock_irqrestore+0x32/0x60 ? process_one_work+0x1c80/0x1c80 ? process_one_work+0x1c80/0x1c80 kthread+0x312/0x3d0 ? kthread_create_worker_on_cpu+0xc0/0xc0 ret_from_fork+0x3a/0x50 Allocated by task 1688: kasan_kmalloc+0xa0/0xd0 __kmalloc+0x162/0x380 u32_change+0x1220/0x3c9e [cls_u32] tc_ctl_tfilter+0x1ba6/0x2f80 rtnetlink_rcv_msg+0x4f0/0x9d0 netlink_rcv_skb+0x124/0x320 netlink_unicast+0x430/0x600 netlink_sendmsg+0x8fa/0xd60 sock_sendmsg+0xb1/0xe0 ___sys_sendmsg+0x678/0x980 __sys_sendmsg+0xc4/0x210 do_syscall_64+0x232/0x7f0 return_from_SYSCALL_64+0x0/0x75 Freed by task 112: kasan_slab_free+0x71/0xc0 kfree+0x114/0x320 rcu_process_callbacks+0xc3f/0x1600 __do_softirq+0x2bf/0xc06 The buggy address belongs to the object at ffff881b83dae600 which belongs to the cache kmalloc-4096 of size 4096 The buggy address is located 24 bytes inside of 4096-byte region [ffff881b83dae600, ffff881b83daf600) The buggy address belongs to the page: page:ffffea006e0f6a00 count:1 mapcount:0 mapping: (null) index:0x0 compound_mapcount: 0 flags: 0x17ffffc0008100(slab|head) raw: 0017ffffc0008100 0000000000000000 0000000000000000 0000000100070007 raw: dead000000000100 dead000000000200 ffff880187c0e600 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff881b83dae500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc ffff881b83dae580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc >ffff881b83dae600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff881b83dae680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff881b83dae700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== The problem is that the htnode is freed before the linked knodes and the latter will try to access the first at u32_destroy_key() time. This change addresses the issue using the htnode refcnt to guarantee the correct free order. While at it also add a RCU annotation, to keep sparse happy. v1 -> v2: use rtnl_derefence() instead of RCU read locks v2 -> v3: - don't check refcnt in u32_destroy_hnode() - cleaned-up u32_destroy() implementation - cleaned-up code comment v3 -> v4: - dropped unneeded comment Reported-by: Li Shuang Fixes: c0d378ef1266 ("net_sched: use tcf_queue_work() in u32 filter") Signed-off-by: Paolo Abeni Acked-by: Cong Wang --- net/sched/cls_u32.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c index e3c5e390ec23..6311a548046b 100644 --- a/net/sched/cls_u32.c +++ b/net/sched/cls_u32.c @@ -398,10 +398,12 @@ static int u32_init(struct tcf_proto *tp) static int u32_destroy_key(struct tcf_proto *tp, struct tc_u_knode *n, bool free_pf) { + struct tc_u_hnode *ht = rtnl_dereference(n->ht_down); + tcf_exts_destroy(&n->exts); tcf_exts_put_net(&n->exts); - if (n->ht_down) - n->ht_down->refcnt--; + if (ht && --ht->refcnt == 0) + kfree(ht); #ifdef CONFIG_CLS_U32_PERF if (free_pf) free_percpu(n->pf); @@ -659,16 +661,15 @@ static void u32_destroy(struct tcf_proto *tp, struct netlink_ext_ack *extack) hlist_del(&tp_c->hnode); - for (ht = rtnl_dereference(tp_c->hlist); - ht; - ht = rtnl_dereference(ht->next)) { - ht->refcnt--; - u32_clear_hnode(tp, ht, extack); - } - while ((ht = rtnl_dereference(tp_c->hlist)) != NULL) { + u32_clear_hnode(tp, ht, extack); RCU_INIT_POINTER(tp_c->hlist, ht->next); - kfree_rcu(ht, rcu); + + /* u32_destroy_key() will later free ht for us, if it's + * still referenced by some knode + */ + if (--ht->refcnt == 0) + kfree_rcu(ht, rcu); } idr_destroy(&tp_c->handle_idr);