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 44592C54E94 for ; Wed, 25 Jan 2023 09:17:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235209AbjAYJRS (ORCPT ); Wed, 25 Jan 2023 04:17:18 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40494 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229646AbjAYJRR (ORCPT ); Wed, 25 Jan 2023 04:17:17 -0500 Received: from mail-pj1-x1032.google.com (mail-pj1-x1032.google.com [IPv6:2607:f8b0:4864:20::1032]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B29A5442D5 for ; Wed, 25 Jan 2023 01:17:15 -0800 (PST) Received: by mail-pj1-x1032.google.com with SMTP id v6-20020a17090ad58600b00229eec90a7fso3552415pju.0 for ; Wed, 25 Jan 2023 01:17:15 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=theori.io; s=google; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=gsKbVhVnx0njFcklhi7O49JD2xBoFLfKAag33RndUgY=; b=S7LdmvUT5Y7K4hKyJoygmPxBbsPpNKVKOEGMNF20XQEQfEd1W23zSwvG2JLudqi7Nn 1mHGjBLkA4H8qn2IcDlOjZ8xCZMbBsLwoQql7A/Xcn4TxXa6Mbjd17yv1NG55NIDDmj2 mhqlFvosvkOZosgoJ+Iph2AeoA0fVPoVbzSNE= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=gsKbVhVnx0njFcklhi7O49JD2xBoFLfKAag33RndUgY=; b=okGHsR1Ds7s5jDkkg6GZINb425O9wwGv+vf5uScrrIL6/QjWE4B05bWOzJk/BC24CQ aCZ3y8PEvgikGuPP839FhUhK8ORGuVxh370o6HFEHhu7OIPU6ZLx+rhg5uMz/mBosvx4 6fgfIYoum/L5H/++V1s0Y+gc4ktLzhYnwZi3E/M9rSgVgfRlV8HiK2OLsB43fGKILYtJ HGp/qInVGopNVX2S3/En2KuHiQ9rIEPxzYYEPoWJQiWFNK8rdLDozpTWrv/cOY/3L8yO mtN2w7Hr8r1MrpPYbE9tXWpDXgzgLnjYjphjMlBs8V+Z/J/0gYpUnRQE93vJfB9KiL2e haaA== X-Gm-Message-State: AFqh2koKLQrDUzuSb7pui+oS1xExlBgyoz6pOGBtBQhlhwszf8xTtvTt olo3IYJ85aX+KWg+571WCG5bzw== X-Google-Smtp-Source: AMrXdXuwgVZBfXVj1gkO9HjAe5s2iGMdEGA57uF3eMVqm5ger8qAGgLmjZflATCRmLSuwHMriYnQIQ== X-Received: by 2002:a17:902:eb89:b0:194:997d:7735 with SMTP id q9-20020a170902eb8900b00194997d7735mr30346613plg.48.1674638235109; Wed, 25 Jan 2023 01:17:15 -0800 (PST) Received: from ubuntu ([39.115.108.115]) by smtp.gmail.com with ESMTPSA id k11-20020a170902760b00b0018997f6fc88sm3142669pll.34.2023.01.25.01.17.12 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Jan 2023 01:17:14 -0800 (PST) Date: Wed, 25 Jan 2023 01:17:10 -0800 From: Hyunwoo Kim To: Kuniyuki Iwashima Cc: davem@davemloft.net, edumazet@google.com, v4bel@theori.io, imv4bel@gmail.com, kuba@kernel.org, linux-hams@vger.kernel.org, netdev@vger.kernel.org, pabeni@redhat.com, ralf@linux-mips.org, syzbot+caa188bdfc1eeafeb418@syzkaller.appspotmail.com Subject: Re: [PATCH v2] netrom: Fix use-after-free caused by accept on already connected socket Message-ID: <20230125091710.GA130922@ubuntu> References: <20230123172233.GA112231@ubuntu> <20230125014347.65971-1-kuniyu@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230125014347.65971-1-kuniyu@amazon.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Tue, Jan 24, 2023 at 05:43:47PM -0800, Kuniyuki Iwashima wrote: > 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 you're right. I misanalyzed nr_rx_frame(). sorry. > > > > 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) IMHO, I think this `close(accepted_socket)` is a necessary procedure. This is because `case NR_STATE_3:` in nr_release() is executed here, and nr_write_internal(sk, NR_DISCREQ) ~ nr_disconnect() sets socket_1's sk to NR_STATE_0. If sk of socket_1 is not set to NR_STATE_0, `case NR_STATE_3:` is executed instead of `case NR_STATE_0:` in `close(socket_1)` and sk is not released. This means you will not be able to trigger UAF on close(uaf_socket). What do you think? So the modified flow chart looks like this: ``` cpu0 cpu1 1. socket_2 = socket(AF_NETROM) . . listen(socket_2) accepted_socket = accept(socket_2) 2. socket_1 = socket(AF_NETROM) nr_create() // sk refcount : 1 connect(socket_1) nr_connect() nr_establish_data_link() nr_write_internal() nr_transmit_buffer() nr_route_frame() nr_loopback_queue() nr_loopback_timer() nr_rx_frame() nr_process_rx_frame() nr_state1_machine() nr->state = NR_STATE_3; 3. write(accepted_socket) nr_sendmsg() nr_output() nr_kick() nr_send_iframe() nr_transmit_buffer() nr_route_frame() nr_loopback_queue() nr_loopback_timer() nr_process_rx_frame(sk, skb); // sk : socket_1's sk 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 : socket_1's sk->sk_receive_queue 4. listen(socket_1) nr_listen() uaf_socket = accept(socket_1) nr_accept() skb_dequeue(&sk->sk_receive_queue); 5. close(accepted_socket) 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; 6. 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 ``` Anything wrong? > > > 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