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 AC268C25B50 for ; Mon, 23 Jan 2023 18:22:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232366AbjAWSWe (ORCPT ); Mon, 23 Jan 2023 13:22:34 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:32836 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232412AbjAWSWd (ORCPT ); Mon, 23 Jan 2023 13:22:33 -0500 Received: from mail-pj1-x1036.google.com (mail-pj1-x1036.google.com [IPv6:2607:f8b0:4864:20::1036]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2AA2430E9B for ; Mon, 23 Jan 2023 10:22:15 -0800 (PST) Received: by mail-pj1-x1036.google.com with SMTP id h5-20020a17090a9c0500b0022bb85eb35dso7385704pjp.3 for ; Mon, 23 Jan 2023 10:22:15 -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=riu7lmExXiJ2g1cdrzPkKrtwD7qEg7W+9CGJJm/D43w=; b=JR9OEoRKm/p7QrkSX5tccJ+UhggycXNB+v5+zFOWCnaEBWRX0Cr7XERqy/Dav003Se FG8ElkD3zFrfLCKpsr4LsHeYPkyya5RuVRJEbxoaSfsT+lhStlisMCAL/IPvffHJt8Kz ppHK3u15IsBErsUM3dtv8x+CpfWs3Vra7ce5w= 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=riu7lmExXiJ2g1cdrzPkKrtwD7qEg7W+9CGJJm/D43w=; b=PiqvJ+bv7KbC7CuC0zMSkKT8NNMXwn8bg+pwkAwOA30sdwfxK33YdzlwGAEuoJEl73 cn0IYAN2f3x0c115TlW0sKhIsOPicRMhVNx7VIe7Tr5/MHpVHBTvfQssin6EgFaAec5+ HHPtBxKhntdM6NP5hKtYX+wRx0L87M/7T1s2qSVHt3cRlRNAxzihws7CveT9M8uNOjgJ dub19s31PUehu+SCQH50PcMdKEfILqlKPXn4w9PYqLtrJp9Jmi48dhvjpkTK8Uj+MP9Y geAx3c4wGop8Sp4gCPzhtL+bfiQjUktVf8X3pyiVBuoylllCdY4l08Vn8/criflKGHDQ CJvw== X-Gm-Message-State: AFqh2koYA//jKzFFMIu5W6jg6r0n/fNifLEPq1eNLrMRtwSebnWFxqAE Ve58yGvnc07+934RcZdX3p28CFVsxqKpIeM0 X-Google-Smtp-Source: AMrXdXtD0Xkmcd6be7f9odNmVDAmpgczK+MJlsdYRH93xfodNj6rNZiTczpvizh/IoqLJjvcVFOGaA== X-Received: by 2002:a17:902:ea0a:b0:194:7ce2:aa3e with SMTP id s10-20020a170902ea0a00b001947ce2aa3emr32372962plg.52.1674498134620; Mon, 23 Jan 2023 10:22:14 -0800 (PST) Received: from ubuntu ([39.115.108.115]) by smtp.gmail.com with ESMTPSA id x8-20020a170902820800b00185402cfedesm4853pln.246.2023.01.23.10.22.11 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Jan 2023 10:22:14 -0800 (PST) Date: Mon, 23 Jan 2023 10:22:09 -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] netrom: Fix use-after-free caused by accept on already connected socket Message-ID: <20230123182209.GB108558@ubuntu> References: <20230123165706.GA108558@ubuntu> <20230123172457.57812-1-kuniyu@amazon.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230123172457.57812-1-kuniyu@amazon.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Mon, Jan 23, 2023 at 09:24:57AM -0800, Kuniyuki Iwashima wrote: > From: Hyunwoo Kim > Date: Mon, 23 Jan 2023 08:57:06 -0800 > > Hi, > > > > Thank you for your review. > > > > > > On Mon, Jan 23, 2023 at 08:22:00AM -0800, Kuniyuki Iwashima wrote: > > > Hi, > > > > > > Thanks for the patch! > > > > > > From: Hyunwoo Kim > > > Date: Sat, 21 Jan 2023 07:08:59 -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 causes nr_accept() to allocate and return a sock with the > > > > sk of the parent AF_NETROM socket. 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() > > > > nr_transmit_buffer() > > > > nr_route_frame() > > > > nr_loopback_queue() > > > > nr_loopback_timer() > > > > nr_rx_frame() > > > > nr_process_rx_frame() > > > > 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); > > > > > > Sorry, I didn't understand how this is populated by close(accepted_socket), > > > especially how skb->sk is set as socket_1's sk. > > > > When calling close(accepted_socket), accepted_socket is currently in NR_STATE_3 state, > > so nr_release() calls `nr_write_internal(sk, NR_DISCREQ)`. > > In a later flow, nr_rx_frame() is called, where nr_find_socket() is used to get socket_1's sk > > from the global list `nr_list` (Because `circuit_index` and `circuit_id` used for search were index/id of socket_1's sk): > > ``` > > sk = NULL; > > > > if (circuit_index == 0 && circuit_id == 0) { > > if (frametype == NR_CONNACK && flags == NR_CHOKE_FLAG) > > sk = nr_find_peer(peer_circuit_index, peer_circuit_id, src); > > } else { > > if (frametype == NR_CONNREQ) > > sk = nr_find_peer(circuit_index, circuit_id, src); > > else > > sk = nr_find_socket(circuit_index, circuit_id); // here > > } > > ``` > > > > And nr_process_rx_frame(), nr_state3_machine(), nr_disconnect() are executed sequentially, > > and `nr_sk(sk)->state = NR_STATE_0;` is executed, so the state of socket_1 sk becomes NR_STATE_0. > > Right, but nr_process_rx_frame() just sends out NR_DISCACK for > accepted_socket, and nr_disconnect() does not queue skb for socket_1 ? > > IIUC, uaf_socket's sk is the same one with socket_1, but I'm wondering > how the sk is queued up for socket_1's recv queue at 4. As I understand it, you know that socket_1 and uaf_socket's sk are the same, but you're confused about how the accepted_socket's sk of number 4 is equal to socket_1's sk, am I correct? The sk of socket_1 and the sk of accepted_socket are completely different. In the flow chart I made, socket_1 and uaf_socket have the same sk, socket_2 has distinct sk, and accepted_socket has distinct non-overlapping sk. (There are a total of three sks in the flowchart.) The reason accepted_socket can refer to the sk of socket_1 in #4 is that `->your_index` and `->your_id` of the sk of accepted_socket point to the sk of socket_1. As explained before, this index/id is used to get the sk of socket_1. (In flowchart #4, nr_process_rx_frame() is called using the sk of socket_1 retrieved from nr_list, rather than using accepted_socket's own sk) Please let me know if I'm misunderstanding and giving a strange answer. > > > > > > As a result, `5. In close(socket_1)`, the code of `case NR_STATE_0:` of nr_release() is executed > > to free the sk, and finally, by calling `close(uaf_socket)`, UAF occurs by referring to the freed sk. > > > > > > > > > > > > 4. 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; > > > > 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 > > > > > > > > CPU: 0 PID: 5128 Comm: syz-executor564 Not tainted 6.2.0-rc1-syzkaller #0 > > > > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/26/2022 > > > > 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(). > > > > > > > > > > I'd add > > > > > > 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..dcfa606684d7 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_CONNECTED) { > > > > > > I guess the same issue happens for SS_CONNECTING (non-blocking connect()), > > > so this should be > > > > > > if (sock->state != SS_UNCONNECTED) { > > > > > > ? > > > > > > Same for the rose and x25 patches. > > > https://lore.kernel.org/netdev/20230122173957.GA99728@ubuntu/ > > > https://lore.kernel.org/netdev/20230122170925.GA98061@ubuntu/ > > > > you're right. > > I will submit the fixed v2 patches. > > > > Regards, > > Hyunwoo Kim > > > > > > > > > > > Thanks, > > > Kuniyuki > > > > > > > + 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