can: j1939: Fix UAF in j1939_sk_match_filter during setsockopt(SO_J1939_FILTER)

Lock jsk->sk to prevent UAF when setsockopt(..., SO_J1939_FILTER, ...)
modifies jsk->filters while receiving packets.

Following trace was seen on affected system:
==================================================================
BUG: KASAN: slab-use-after-free in j1939_sk_recv_match_one+0x1af/0x2d0 [can_j1939]
Read of size 4 at addr ffff888012144014 by task j1939/350

CPU: 0 PID: 350 Comm: j1939 Tainted: G W OE 6.5.0-rc5 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
print_report+0xd3/0x620
? kasan_complete_mode_report_info+0x7d/0x200
? j1939_sk_recv_match_one+0x1af/0x2d0 [can_j1939]
kasan_report+0xc2/0x100
? j1939_sk_recv_match_one+0x1af/0x2d0 [can_j1939]
__asan_load4+0x84/0xb0
j1939_sk_recv_match_one+0x1af/0x2d0 [can_j1939]
j1939_sk_recv+0x20b/0x320 [can_j1939]
? __kasan_check_write+0x18/0x20
? __pfx_j1939_sk_recv+0x10/0x10 [can_j1939]
? j1939_simple_recv+0x69/0x280 [can_j1939]
? j1939_ac_recv+0x5e/0x310 [can_j1939]
j1939_can_recv+0x43f/0x580 [can_j1939]
? __pfx_j1939_can_recv+0x10/0x10 [can_j1939]
? raw_rcv+0x42/0x3c0 [can_raw]
? __pfx_j1939_can_recv+0x10/0x10 [can_j1939]
can_rcv_filter+0x11f/0x350 [can]
can_receive+0x12f/0x190 [can]
? __pfx_can_rcv+0x10/0x10 [can]
can_rcv+0xdd/0x130 [can]
? __pfx_can_rcv+0x10/0x10 [can]
__netif_receive_skb_one_core+0x13d/0x150
? __pfx___netif_receive_skb_one_core+0x10/0x10
? __kasan_check_write+0x18/0x20
? _raw_spin_lock_irq+0x8c/0xe0
__netif_receive_skb+0x23/0xb0
process_backlog+0x107/0x260
__napi_poll+0x69/0x310
net_rx_action+0x2a1/0x580
? __pfx_net_rx_action+0x10/0x10
? __pfx__raw_spin_lock+0x10/0x10
? handle_irq_event+0x7d/0xa0
__do_softirq+0xf3/0x3f8
do_softirq+0x53/0x80
</IRQ>
<TASK>
__local_bh_enable_ip+0x6e/0x70
netif_rx+0x16b/0x180
can_send+0x32b/0x520 [can]
? __pfx_can_send+0x10/0x10 [can]
? __check_object_size+0x299/0x410
raw_sendmsg+0x572/0x6d0 [can_raw]
? __pfx_raw_sendmsg+0x10/0x10 [can_raw]
? apparmor_socket_sendmsg+0x2f/0x40
? __pfx_raw_sendmsg+0x10/0x10 [can_raw]
sock_sendmsg+0xef/0x100
sock_write_iter+0x162/0x220
? __pfx_sock_write_iter+0x10/0x10
? __rtnl_unlock+0x47/0x80
? security_file_permission+0x54/0x320
vfs_write+0x6ba/0x750
? __pfx_vfs_write+0x10/0x10
? __fget_light+0x1ca/0x1f0
? __rcu_read_unlock+0x5b/0x280
ksys_write+0x143/0x170
? __pfx_ksys_write+0x10/0x10
? __kasan_check_read+0x15/0x20
? fpregs_assert_state_consistent+0x62/0x70
__x64_sys_write+0x47/0x60
do_syscall_64+0x60/0x90
? do_syscall_64+0x6d/0x90
? irqentry_exit+0x3f/0x50
? exc_page_fault+0x79/0xf0
entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Allocated by task 348:
kasan_save_stack+0x2a/0x50
kasan_set_track+0x29/0x40
kasan_save_alloc_info+0x1f/0x30
__kasan_kmalloc+0xb5/0xc0
__kmalloc_node_track_caller+0x67/0x160
j1939_sk_setsockopt+0x284/0x450 [can_j1939]
__sys_setsockopt+0x15c/0x2f0
__x64_sys_setsockopt+0x6b/0x80
do_syscall_64+0x60/0x90
entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Freed by task 349:
kasan_save_stack+0x2a/0x50
kasan_set_track+0x29/0x40
kasan_save_free_info+0x2f/0x50
__kasan_slab_free+0x12e/0x1c0
__kmem_cache_free+0x1b9/0x380
kfree+0x7a/0x120
j1939_sk_setsockopt+0x3b2/0x450 [can_j1939]
__sys_setsockopt+0x15c/0x2f0
__x64_sys_setsockopt+0x6b/0x80
do_syscall_64+0x60/0x90
entry_SYSCALL_64_after_hwframe+0x6e/0xd8

Fixes: 9d71dd0c70099 ("can: add support of SAE J1939 protocol")
Reported-by: Sili Luo <[e-mail]>
Suggested-by: Sili Luo <[e-mail]>
Acked-by: Oleksij Rempel <[e-mail]>
Cc: [e-mail]
Signed-off-by: Oleksij Rempel <[e-mail]>
Link: https://lore.kernel.org/all/[e-mail]
Signed-off-by: Marc Kleine-Budde <[e-mail]>

net/can/j1939/j1939-priv.h

···
 
 	int ifindex;
 	struct j1939_addr addr;
+	spinlock_t filters_lock;
 	struct j1939_filter *filters;
 	int nfilters;
 	pgn_t pgn_rx_filter;

net/can/j1939/socket.c

···
 static bool j1939_sk_match_filter(struct j1939_sock *jsk,
 				  const struct j1939_sk_buff_cb *skcb)
 {
-	const struct j1939_filter *f = jsk->filters;
-	int nfilter = jsk->nfilters;
+	const struct j1939_filter *f;
+	int nfilter;
+
+	spin_lock_bh(&jsk->filters_lock);
+
+	f = jsk->filters;
+	nfilter = jsk->nfilters;
 
 	if (!nfilter)
 		/* receive all when no filters are assigned */
-		return true;
+		goto filter_match_found;
 
 	for (; nfilter; ++f, --nfilter) {
 		if ((skcb->addr.pgn & f->pgn_mask) != f->pgn)
···
 			continue;
 		if ((skcb->addr.src_name & f->name_mask) != f->name)
 			continue;
-		return true;
+		goto filter_match_found;
 	}
+
+	spin_unlock_bh(&jsk->filters_lock);
 	return false;
+
+filter_match_found:
+	spin_unlock_bh(&jsk->filters_lock);
+	return true;
 }
 
 static bool j1939_sk_recv_match_one(struct j1939_sock *jsk,
···
 	atomic_set(&jsk->skb_pending, 0);
 	spin_lock_init(&jsk->sk_session_queue_lock);
 	INIT_LIST_HEAD(&jsk->sk_session_queue);
+	spin_lock_init(&jsk->filters_lock);
 
 	/* j1939_sk_sock_destruct() depends on SOCK_RCU_FREE flag */
 	sock_set_flag(sk, SOCK_RCU_FREE);
···
 		}
 
 		lock_sock(&jsk->sk);
+		spin_lock_bh(&jsk->filters_lock);
 		ofilters = jsk->filters;
 		jsk->filters = filters;
 		jsk->nfilters = count;
+		spin_unlock_bh(&jsk->filters_lock);
 		release_sock(&jsk->sk);
 		kfree(ofilters);
 		return 0;