From 409db27e3a2eb5e8ef7226ca33be33361b3ed1c9 Mon Sep 17 00:00:00 2001
From: Kuniyuki Iwashima <kuniyu@amazon.com>
Date: Fri, 20 Jan 2023 15:19:27 -0800
Subject: [PATCH] netrom: Fix use-after-free of a listening socket.
Git-commit: 409db27e3a2eb5e8ef7226ca33be33361b3ed1c9
Patch-mainline: v6.2-rc6
References: git-fixes
syzbot reported a use-after-free in do_accept(), precisely nr_accept()
as sk_prot_alloc() allocated the memory and sock_put() frees it. [0]
The issue could happen if the heartbeat timer is fired and
nr_heartbeat_expiry() calls nr_destroy_socket(), where a socket
has SOCK_DESTROY or a listening socket has SOCK_DEAD.
In this case, the first condition cannot be true. SOCK_DESTROY is
flagged in nr_release() only when the file descriptor is close()d,
but accept() is being called for the listening socket, so the second
condition must be true.
Usually, the AF_NETROM listener neither starts timers nor sets
SOCK_DEAD. However, the condition is met if connect() fails before
listen(). connect() starts the t1 timer and heartbeat timer, and
t1timer calls nr_disconnect() when timeout happens. Then, SOCK_DEAD
is set, and if we call listen(), the heartbeat timer calls
nr_destroy_socket().
nr_connect
nr_establish_data_link(sk)
nr_start_t1timer(sk)
nr_start_heartbeat(sk)
nr_t1timer_expiry
nr_disconnect(sk, ETIMEDOUT)
nr_sk(sk)->state = NR_STATE_0
sk->sk_state = TCP_CLOSE
sock_set_flag(sk, SOCK_DEAD)
nr_listen
if (sk->sk_state != TCP_LISTEN)
sk->sk_state = TCP_LISTEN
nr_heartbeat_expiry
switch (nr->state)
case NR_STATE_0
if (sk->sk_state == TCP_LISTEN &&
sock_flag(sk, SOCK_DEAD))
nr_destroy_socket(sk)
This path seems expected, and nr_destroy_socket() is called to clean
up resources. Initially, there was sock_hold() before nr_destroy_socket()
so that the socket would not be freed, but the commit 517a16b1a88b
("netrom: Decrease sock refcount when sock timers expire") accidentally
removed it.
To fix use-after-free, let's add sock_hold().
[0]:
Bug: KASAN: use-after-free in do_accept+0x483/0x510 net/socket.c:1848
Read of size 8 at addr ffff88807978d398 by task syz-executor.3/5315
Cpu: 0 PID: 5315 Comm: syz-executor.3 Not tainted 6.2.0-rc3-syzkaller-00165-gd9fc1511728c #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
do_accept+0x483/0x510 net/socket.c:1848
__sys_accept4_file net/socket.c:1897 [inline]
__sys_accept4+0x9a/0x120 net/socket.c:1927
__do_sys_accept net/socket.c:1944 [inline]
__se_sys_accept net/socket.c:1941 [inline]
__x64_sys_accept+0x75/0xb0 net/socket.c:1941
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
Rip: 0033:0x7fa436a8c0c9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 00 00 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48
Rsp: 002b:00007fa437784168 EFLAGS: 00000246 ORIG_RAX: 000000000000002b
Rax: ffffffffffffffda RBX: 00007fa436bac050 RCX: 00007fa436a8c0c9
Rdx: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000005
Rbp: 00007fa436ae7ae9 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffebc6700df R14: 00007fa437784300 R15: 0000000000022000 </TASK>
Allocated by task 5294:
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 14:
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_heartbeat_expiry+0x1d7/0x460 net/netrom/nr_timer.c:148
call_timer_fn+0x1da/0x7c0 kernel/time/timer.c:1700
expire_timers+0x2c6/0x5c0 kernel/time/timer.c:1751
__run_timers kernel/time/timer.c:2022 [inline]
__run_timers kernel/time/timer.c:1995 [inline]
run_timer_softirq+0x326/0x910 kernel/time/timer.c:2035
__do_softirq+0x1fb/0xadc kernel/softirq.c:571
Fixes: 517a16b1a88b ("netrom: Decrease sock refcount when sock timers expire")
Reported-by: syzbot+5fafd5cfe1fc91f6b352@syzkaller.appspotmail.com
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20230120231927.51711-1-kuniyu@amazon.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
net/netrom/nr_timer.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/net/netrom/nr_timer.c b/net/netrom/nr_timer.c
index a8da88db7893..4e7c968cde2d 100644
--- a/net/netrom/nr_timer.c
+++ b/net/netrom/nr_timer.c
@@ -121,6 +121,7 @@ static void nr_heartbeat_expiry(struct timer_list *t)
is accepted() it isn't 'dead' so doesn't get removed. */
if (sock_flag(sk, SOCK_DESTROY) ||
(sk->sk_state == TCP_LISTEN && sock_flag(sk, SOCK_DEAD))) {
+ sock_hold(sk);
bh_unlock_sock(sk);
nr_destroy_socket(sk);
goto out;
--
2.35.3