* [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
@ 2023-01-21 15:08 Hyunwoo Kim
2023-01-21 15:12 ` Hyunwoo Kim
2023-01-23 16:22 ` Kuniyuki Iwashima
0 siblings, 2 replies; 7+ messages in thread
From: Hyunwoo Kim @ 2023-01-21 15:08 UTC (permalink / raw)
To: ralf, davem, edumazet, kuba, pabeni
Cc: v4bel, imv4bel, linux-hams, netdev, syzbot+caa188bdfc1eeafeb418
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
^ permalink raw reply related [flat|nested] 7+ messages in thread
* Re: [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
2023-01-21 15:08 [PATCH] netrom: Fix use-after-free caused by accept on already connected socket Hyunwoo Kim
@ 2023-01-21 15:12 ` Hyunwoo Kim
2023-01-23 16:22 ` Kuniyuki Iwashima
1 sibling, 0 replies; 7+ messages in thread
From: Hyunwoo Kim @ 2023-01-21 15:12 UTC (permalink / raw)
To: ralf, davem, edumazet, kuba, pabeni
Cc: imv4bel, linux-hams, netdev, syzbot+caa188bdfc1eeafeb418
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
2023-01-21 15:08 [PATCH] netrom: Fix use-after-free caused by accept on already connected socket Hyunwoo Kim
2023-01-21 15:12 ` Hyunwoo Kim
@ 2023-01-23 16:22 ` Kuniyuki Iwashima
2023-01-23 16:57 ` Hyunwoo Kim
1 sibling, 1 reply; 7+ messages in thread
From: Kuniyuki Iwashima @ 2023-01-23 16:22 UTC (permalink / raw)
To: v4bel
Cc: davem, edumazet, imv4bel, kuba, linux-hams, netdev, pabeni, ralf,
syzbot+caa188bdfc1eeafeb418, kuniyu
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
2023-01-23 16:22 ` Kuniyuki Iwashima
@ 2023-01-23 16:57 ` Hyunwoo Kim
2023-01-23 17:24 ` Kuniyuki Iwashima
0 siblings, 1 reply; 7+ messages in thread
From: Hyunwoo Kim @ 2023-01-23 16:57 UTC (permalink / raw)
To: Kuniyuki Iwashima
Cc: davem, edumazet, v4bel, imv4bel, kuba, linux-hams, netdev,
pabeni, ralf, syzbot+caa188bdfc1eeafeb418
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
2023-01-23 16:57 ` Hyunwoo Kim
@ 2023-01-23 17:24 ` Kuniyuki Iwashima
2023-01-23 18:22 ` Hyunwoo Kim
0 siblings, 1 reply; 7+ messages in thread
From: Kuniyuki Iwashima @ 2023-01-23 17:24 UTC (permalink / raw)
To: v4bel
Cc: davem, edumazet, imv4bel, kuba, kuniyu, linux-hams, netdev,
pabeni, ralf, syzbot+caa188bdfc1eeafeb418
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
2023-01-23 17:24 ` Kuniyuki Iwashima
@ 2023-01-23 18:22 ` Hyunwoo Kim
2023-01-23 19:27 ` Kuniyuki Iwashima
0 siblings, 1 reply; 7+ messages in thread
From: Hyunwoo Kim @ 2023-01-23 18:22 UTC (permalink / raw)
To: Kuniyuki Iwashima
Cc: davem, edumazet, v4bel, imv4bel, kuba, linux-hams, netdev,
pabeni, ralf, syzbot+caa188bdfc1eeafeb418
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
^ permalink raw reply [flat|nested] 7+ messages in thread
* Re: [PATCH] netrom: Fix use-after-free caused by accept on already connected socket
2023-01-23 18:22 ` Hyunwoo Kim
@ 2023-01-23 19:27 ` Kuniyuki Iwashima
0 siblings, 0 replies; 7+ messages in thread
From: Kuniyuki Iwashima @ 2023-01-23 19:27 UTC (permalink / raw)
To: v4bel
Cc: davem, edumazet, imv4bel, kuba, kuniyu, linux-hams, netdev,
pabeni, ralf, syzbot+caa188bdfc1eeafeb418
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
^ permalink raw reply [flat|nested] 7+ messages in thread
end of thread, other threads:[~2023-01-23 19:28 UTC | newest]
Thread overview: 7+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2023-01-21 15:08 [PATCH] netrom: Fix use-after-free caused by accept on already connected socket Hyunwoo Kim
2023-01-21 15:12 ` Hyunwoo Kim
2023-01-23 16:22 ` Kuniyuki Iwashima
2023-01-23 16:57 ` Hyunwoo Kim
2023-01-23 17:24 ` Kuniyuki Iwashima
2023-01-23 18:22 ` Hyunwoo Kim
2023-01-23 19:27 ` Kuniyuki Iwashima
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