| Message ID | 20230121150859.GA9817@ubuntu (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | netrom: Fix use-after-free caused by accept on already connected socket | expand |
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: > <TASK> > __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 > </TASK> > > 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 <v4bel@theori.io> > --- > 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
Hi, Thanks for the patch! From: Hyunwoo Kim <v4bel@theori.io> 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. > 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: > <TASK> > __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 > </TASK> > > 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 <v4bel@theori.io> > --- > 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/ 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
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 <v4bel@theori.io> > 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. 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: > > <TASK> > > __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 > > </TASK> > > > > 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 <v4bel@theori.io> > > --- > > 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
From: Hyunwoo Kim <v4bel@theori.io> 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 <v4bel@theori.io> > > 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 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: > > > <TASK> > > > __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 > > > </TASK> > > > > > > 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 <v4bel@theori.io> > > > --- > > > 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
On Mon, Jan 23, 2023 at 09:24:57AM -0800, Kuniyuki Iwashima wrote: > From: Hyunwoo Kim <v4bel@theori.io> > 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 <v4bel@theori.io> > > > 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: > > > > <TASK> > > > > __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 > > > > </TASK> > > > > > > > > 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 <v4bel@theori.io> > > > > --- > > > > 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
From: Hyunwoo Kim <v4bel@theori.io> Date: Mon, 23 Jan 2023 10:22:09 -0800 > On Mon, Jan 23, 2023 at 09:24:57AM -0800, Kuniyuki Iwashima wrote: > > From: Hyunwoo Kim <v4bel@theori.io> > > 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 <v4bel@theori.io> > > > > 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? No. I'm not sure how close(accepeted_socket) populates socket_1's sk_receive_queue by a skb->sk with socket_1's sk so that uaf_socket has the same sk with socket_1. > > 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) I understand this, but to make "uaf_socket = accept(socket_1)" happen, we need to put a skb in socket_1's recv_q in 4. with the found sk. As you said, 4. finds the sk by nr_find_socket() (as not listener) and ends up calling nr_process_rx_frame(), which does not queue the skb with the sk for socket_1's queue, right ? In short, where is a skb created with socket_1's sk and queued for socket_1's recv_q ? We don't call sock_queue_rcv_skb() at 4. > > 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: > > > > > <TASK> > > > > > __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 > > > > > </TASK> > > > > > > > > > > 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 <v4bel@theori.io> > > > > > --- > > > > > 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
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;
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: <TASK> __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 </TASK> 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 <v4bel@theori.io> --- net/netrom/af_netrom.c | 5 +++++ 1 file changed, 5 insertions(+)