From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hyunwoo Kim Subject: Re: [PATCH] netrom: Fix use-after-free caused by accept on already connected socket Date: Sat, 21 Jan 2023 07:12:27 -0800 Message-ID: <20230121151227.GA9907@ubuntu> References: <20230121150859.GA9817@ubuntu> Mime-Version: 1.0 Return-path: 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=vhLg/NccQIbYS88/cxO9nYQLbfpzqVllO2E1gziu1e8=; b=C7NL6GLmd0U/chGijSaigUCtNfOnQbLJ57fswl4/KfeOFNbCAyu5pASwhGEaGxHIR7 w16F6Z157TEj1ldXFoQ9L8fS0vUBBLkZWWj8pwTagJv/R9aI8cJ4O+xiz+aX5iqgFV8W WwsKkLb4sHVBNVbgvxar1DjZSfxvX+c7WQnRc= Content-Disposition: inline In-Reply-To: <20230121150859.GA9817@ubuntu> List-ID: Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: ralf@linux-mips.org, davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com Cc: imv4bel@gmail.com, linux-hams@vger.kernel.org, netdev@vger.kernel.org, syzbot+caa188bdfc1eeafeb418@syzkaller.appspotmail.com On Sat, Jan 21, 2023 at 07:08:59AM -0800, Hyunwoo Kim wrote: > 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); > 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(). > > 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) { > + 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 > Dear, Looks like a patch was recently submitted for another use-after-free bug in netrom: https://lore.kernel.org/all/20230120231927.51711-1-kuniyu@amazon.com/ However, the connect -> accept bug I reported is unaffected by the above patch and still occurs. Regards, Hyunwoo Kim