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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 108C6C38142 for ; Wed, 25 Jan 2023 01:44:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229953AbjAYBoK (ORCPT ); Tue, 24 Jan 2023 20:44:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41368 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229528AbjAYBoJ (ORCPT ); Tue, 24 Jan 2023 20:44:09 -0500 Received: from smtp-fw-6002.amazon.com (smtp-fw-6002.amazon.com [52.95.49.90]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 79EF83B673; Tue, 24 Jan 2023 17:44:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1674611046; x=1706147046; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=M+9PM90yLTTWoFED9PJLZGWhfuZqmXtjOyIWn6YVHsc=; b=rnwakZ3J2qOXs6cjkVcB54ibNUgwpKwI6h45Q2zQ5F9bpwnoqGjfogru Woh/FWVjx8HVT8bLE6pgC1fW8CBDINwzFVEcay5Y3ZTrwS1ThyA/ETQuW 5xgfHwsz2ZKcoZPgu6pnFZW9raRld0z/PcNoynwOJkpNlXnwhYUn8UXop g=; X-IronPort-AV: E=Sophos;i="5.97,244,1669075200"; d="scan'208";a="290089851" Received: from iad12-co-svc-p1-lb1-vlan3.amazon.com (HELO email-inbound-relay-iad-1d-m6i4x-25ac6bd5.us-east-1.amazon.com) ([10.43.8.6]) by smtp-border-fw-6002.iad6.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Jan 2023 01:44:04 +0000 Received: from EX13MTAUWB002.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan2.iad.amazon.com [10.40.163.34]) by email-inbound-relay-iad-1d-m6i4x-25ac6bd5.us-east-1.amazon.com (Postfix) with ESMTPS id 291AF4329F; Wed, 25 Jan 2023 01:44:01 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB002.ant.amazon.com (10.43.161.202) with Microsoft SMTP Server (TLS) id 15.0.1497.45; Wed, 25 Jan 2023 01:43:59 +0000 Received: from 88665a182662.ant.amazon.com (10.43.160.120) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.7; Wed, 25 Jan 2023 01:43:56 +0000 From: Kuniyuki Iwashima To: CC: , , , , , , , , , Subject: Re: [PATCH v2] netrom: Fix use-after-free caused by accept on already connected socket Date: Tue, 24 Jan 2023 17:43:47 -0800 Message-ID: <20230125014347.65971-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20230123172233.GA112231@ubuntu> References: <20230123172233.GA112231@ubuntu> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.43.160.120] X-ClientProxiedBy: EX13D36UWB002.ant.amazon.com (10.43.161.149) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org Hi, I think the diff looks good but changelog is not correct. From: Hyunwoo Kim Date: Mon, 23 Jan 2023 09:22:33 -0800 > If listen() and accept() are called on an AF_NETROM socket that > has already been connect()ed, accept() succeeds in connecting. > This is because nr_accept() dequeues the skb queued in > `sk->sk_receive_queue` in nr_connect(). This sentence is misleading. The skb sent by nr_connect() is queued up for the peer's sk_receive_queue (socket_2 below), and also the reply is not queued for connect()er (socket_1) because it is NR_CONNACK and just consumed by nr_state1_machine() to transition to NR_STATE_3 and TCP_ESTABLISHED. > > This causes nr_accept() to allocate and return a sock with the > sk of the parent AF_NETROM socket. This happens because the peer (socket_2) sends some data by nr_sendmsg(), whose type is NR_INFO and the data is queued up for the connect()er's (socket_1) sk_receive_queue by - nr_state3_machine - nr_queue_rx_frame - sock_queue_rcv_skb > And here's where use-after-free > can happen through complex race conditions: > ``` > cpu0 cpu1 > 1. socket_2 = socket(AF_NETROM) > listen(socket_2) > accepted_socket = accept(socket_2) // loopback connection with socket_1 > 2. socket_1 = socket(AF_NETROM) > nr_create() // sk refcount : 1 > connect(socket_1) // loopback connection with socket_2 > nr_connect() > nr_establish_data_link() > nr_write_internal() This is NR_CONNREQ for socket_2. > nr_transmit_buffer() > nr_route_frame() > nr_loopback_queue() > nr_loopback_timer() > nr_rx_frame() > nr_process_rx_frame() So, nr_process_rx_frame() is not called from nr_rx_frame() because the kernel finds socket_2 by nr_find_listener(), and creates accepted_socket, and then responds with NR_CONNACK to socket_1. And accepted_socket sends some data with NR_INFO, then, nr_state3_machine() is called for socket_1 and the skb with sk pointing socket_1 is queued for socket_1's sk_receive_queue. I think this part is lacking in this UAF scenario. What do you think ? > nr_state3_machine() > nr_queue_rx_frame() > sock_queue_rcv_skb() > sock_queue_rcv_skb_reason() > __sock_queue_rcv_skb() > __skb_queue_tail(list, skb); // list : sk->sk_receive_queue > > 3. listen(socket_1) > nr_listen() > uaf_socket = accept(socket_1) > nr_accept() > skb_dequeue(&sk->sk_receive_queue); > 4. close(accepted_socket) And I guess this close() is not so important in this case. Even if we don't close the socket cleanly, the UAF will happen, right ? (it might be caused in a different place like timer though) > nr_release() > nr_write_internal(sk, NR_DISCREQ) > nr_transmit_buffer() // NR_DISCREQ > nr_route_frame() > nr_loopback_queue() > nr_loopback_timer() > nr_rx_frame() // sk : socket_1's sk > nr_process_rx_frame() // NR_STATE_3 > nr_state3_machine() // NR_DISCREQ > nr_disconnect() > nr_sk(sk)->state = NR_STATE_0; > 5. close(socket_1) // sk refcount : 3 > nr_release() // NR_STATE_0 > sock_put(sk); // sk refcount : 0 > sk_free(sk); > close(uaf_socket) > nr_release() > sock_hold(sk); // UAF > ``` > > KASAN report by syzbot: > ``` > BUG: KASAN: use-after-free in nr_release+0x66/0x460 net/netrom/af_netrom.c:520 > Write of size 4 at addr ffff8880235d8080 by task syz-executor564/5128 > > Call Trace: > > __dump_stack lib/dump_stack.c:88 [inline] > dump_stack_lvl+0xd1/0x138 lib/dump_stack.c:106 > print_address_description mm/kasan/report.c:306 [inline] > print_report+0x15e/0x461 mm/kasan/report.c:417 > kasan_report+0xbf/0x1f0 mm/kasan/report.c:517 > check_region_inline mm/kasan/generic.c:183 [inline] > kasan_check_range+0x141/0x190 mm/kasan/generic.c:189 > instrument_atomic_read_write include/linux/instrumented.h:102 [inline] > atomic_fetch_add_relaxed include/linux/atomic/atomic-instrumented.h:116 [inline] > __refcount_add include/linux/refcount.h:193 [inline] > __refcount_inc include/linux/refcount.h:250 [inline] > refcount_inc include/linux/refcount.h:267 [inline] > sock_hold include/net/sock.h:775 [inline] > nr_release+0x66/0x460 net/netrom/af_netrom.c:520 > __sock_release+0xcd/0x280 net/socket.c:650 > sock_close+0x1c/0x20 net/socket.c:1365 > __fput+0x27c/0xa90 fs/file_table.c:320 > task_work_run+0x16f/0x270 kernel/task_work.c:179 > exit_task_work include/linux/task_work.h:38 [inline] > do_exit+0xaa8/0x2950 kernel/exit.c:867 > do_group_exit+0xd4/0x2a0 kernel/exit.c:1012 > get_signal+0x21c3/0x2450 kernel/signal.c:2859 > arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306 > exit_to_user_mode_loop kernel/entry/common.c:168 [inline] > exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 > __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] > syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 > do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > RIP: 0033:0x7f6c19e3c9b9 > Code: Unable to access opcode bytes at 0x7f6c19e3c98f. > RSP: 002b:00007fffd4ba2ce8 EFLAGS: 00000246 ORIG_RAX: 0000000000000133 > RAX: 0000000000000116 RBX: 0000000000000003 RCX: 00007f6c19e3c9b9 > RDX: 0000000000000318 RSI: 00000000200bd000 RDI: 0000000000000006 > RBP: 0000000000000003 R08: 000000000000000d R09: 000000000000000d > R10: 0000000000000000 R11: 0000000000000246 R12: 000055555566a2c0 > R13: 0000000000000011 R14: 0000000000000000 R15: 0000000000000000 > > > Allocated by task 5128: > kasan_save_stack+0x22/0x40 mm/kasan/common.c:45 > kasan_set_track+0x25/0x30 mm/kasan/common.c:52 > ____kasan_kmalloc mm/kasan/common.c:371 [inline] > ____kasan_kmalloc mm/kasan/common.c:330 [inline] > __kasan_kmalloc+0xa3/0xb0 mm/kasan/common.c:380 > kasan_kmalloc include/linux/kasan.h:211 [inline] > __do_kmalloc_node mm/slab_common.c:968 [inline] > __kmalloc+0x5a/0xd0 mm/slab_common.c:981 > kmalloc include/linux/slab.h:584 [inline] > sk_prot_alloc+0x140/0x290 net/core/sock.c:2038 > sk_alloc+0x3a/0x7a0 net/core/sock.c:2091 > nr_create+0xb6/0x5f0 net/netrom/af_netrom.c:433 > __sock_create+0x359/0x790 net/socket.c:1515 > sock_create net/socket.c:1566 [inline] > __sys_socket_create net/socket.c:1603 [inline] > __sys_socket_create net/socket.c:1588 [inline] > __sys_socket+0x133/0x250 net/socket.c:1636 > __do_sys_socket net/socket.c:1649 [inline] > __se_sys_socket net/socket.c:1647 [inline] > __x64_sys_socket+0x73/0xb0 net/socket.c:1647 > do_syscall_x64 arch/x86/entry/common.c:50 [inline] > do_syscall_64+0x39/0xb0 arch/x86/entry/common.c:80 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > > Freed by task 5128: > kasan_save_stack+0x22/0x40 mm/kasan/common.c:45 > kasan_set_track+0x25/0x30 mm/kasan/common.c:52 > kasan_save_free_info+0x2b/0x40 mm/kasan/generic.c:518 > ____kasan_slab_free mm/kasan/common.c:236 [inline] > ____kasan_slab_free+0x13b/0x1a0 mm/kasan/common.c:200 > kasan_slab_free include/linux/kasan.h:177 [inline] > __cache_free mm/slab.c:3394 [inline] > __do_kmem_cache_free mm/slab.c:3580 [inline] > __kmem_cache_free+0xcd/0x3b0 mm/slab.c:3587 > sk_prot_free net/core/sock.c:2074 [inline] > __sk_destruct+0x5df/0x750 net/core/sock.c:2166 > sk_destruct net/core/sock.c:2181 [inline] > __sk_free+0x175/0x460 net/core/sock.c:2192 > sk_free+0x7c/0xa0 net/core/sock.c:2203 > sock_put include/net/sock.h:1991 [inline] > nr_release+0x39e/0x460 net/netrom/af_netrom.c:554 > __sock_release+0xcd/0x280 net/socket.c:650 > sock_close+0x1c/0x20 net/socket.c:1365 > __fput+0x27c/0xa90 fs/file_table.c:320 > task_work_run+0x16f/0x270 kernel/task_work.c:179 > exit_task_work include/linux/task_work.h:38 [inline] > do_exit+0xaa8/0x2950 kernel/exit.c:867 > do_group_exit+0xd4/0x2a0 kernel/exit.c:1012 > get_signal+0x21c3/0x2450 kernel/signal.c:2859 > arch_do_signal_or_restart+0x79/0x5c0 arch/x86/kernel/signal.c:306 > exit_to_user_mode_loop kernel/entry/common.c:168 [inline] > exit_to_user_mode_prepare+0x15f/0x250 kernel/entry/common.c:203 > __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline] > syscall_exit_to_user_mode+0x1d/0x50 kernel/entry/common.c:296 > do_syscall_64+0x46/0xb0 arch/x86/entry/common.c:86 > entry_SYSCALL_64_after_hwframe+0x63/0xcd > ``` > > To fix this problem, nr_listen() returns -EINVAL for sockets that successfully nr_connect(). > > Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") > Reported-by: syzbot+caa188bdfc1eeafeb418@syzkaller.appspotmail.com > Signed-off-by: Hyunwoo Kim > --- > net/netrom/af_netrom.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/net/netrom/af_netrom.c b/net/netrom/af_netrom.c > index 6f7f4392cffb..5a4cb796150f 100644 > --- a/net/netrom/af_netrom.c > +++ b/net/netrom/af_netrom.c > @@ -400,6 +400,11 @@ static int nr_listen(struct socket *sock, int backlog) > struct sock *sk = sock->sk; > > lock_sock(sk); > + if (sock->state != SS_UNCONNECTED) { > + release_sock(sk); > + return -EINVAL; > + } > + > if (sk->sk_state != TCP_LISTEN) { > memset(&nr_sk(sk)->user_addr, 0, AX25_ADDR_LEN); > sk->sk_max_ack_backlog = backlog; > -- > 2.25.1