------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 9554 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 1 UID: 0 PID: 9554 Comm: syz.1.709 Not tainted 6.12.0-rc1-syzkaller-00046-g7ec462100ef9 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 88 13 00 fd 84 db 0f 85 66 ff ff ff e8 9b 11 00 fd c6 05 db 99 ba 0b 01 90 48 c7 c7 80 3e d1 8b e8 37 fb c0 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 78 11 00 fd 0f b6 1d b6 99 ba 0b 31
RSP: 0018:ffffc90000a18940 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff814e7329
RDX: ffff888029b03c00 RSI: ffffffff814e7336 RDI: 0000000000000001
RBP: ffff88807bf1a864 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
R13: 0000000000000000 R14: ffff88807bf1a864 R15: 0000000000000001
FS:  00007fb8465c26c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007feebf0c1000 CR3: 0000000053c0a000 CR4: 0000000000350ef0
Call Trace:
 <IRQ>
 __refcount_sub_and_test include/linux/refcount.h:275 [inline]
 __refcount_dec_and_test include/linux/refcount.h:307 [inline]
 refcount_dec_and_test include/linux/refcount.h:325 [inline]
 skb_unref include/linux/skbuff.h:1232 [inline]
 __sk_skb_reason_drop net/core/skbuff.c:1213 [inline]
 sk_skb_reason_drop+0x183/0x1a0 net/core/skbuff.c:1241
 kfree_skb_reason include/linux/skbuff.h:1262 [inline]
 kfree_skb include/linux/skbuff.h:1271 [inline]
 j1939_session_destroy+0x163/0x460 net/can/j1939/transport.c:282
 __j1939_session_release net/can/j1939/transport.c:294 [inline]
 kref_put include/linux/kref.h:65 [inline]
 j1939_session_put net/can/j1939/transport.c:299 [inline]
 j1939_simple_recv+0x43a/0x5c0 net/can/j1939/transport.c:2192
 j1939_can_recv+0x833/0xa50 net/can/j1939/main.c:112
 deliver net/can/af_can.c:572 [inline]
 can_rcv_filter+0x2ab/0x900 net/can/af_can.c:606
 can_receive+0x320/0x5c0 net/can/af_can.c:663
 can_rcv+0x1e2/0x280 net/can/af_can.c:687
 __netif_receive_skb_one_core+0x1b4/0x1e0 net/core/dev.c:5662
 __netif_receive_skb+0x1d/0x160 net/core/dev.c:5775
 process_backlog+0x443/0x15f0 net/core/dev.c:6107
 __napi_poll.constprop.0+0xba/0x550 net/core/dev.c:6771
 napi_poll net/core/dev.c:6840 [inline]
 net_rx_action+0xa92/0x1010 net/core/dev.c:6962
 handle_softirqs+0x216/0x8f0 kernel/softirq.c:554
 do_softirq kernel/softirq.c:455 [inline]
 do_softirq+0xb2/0xf0 kernel/softirq.c:442
 </IRQ>
 <TASK>
 __local_bh_enable_ip+0x100/0x120 kernel/softirq.c:382
 j1939_sk_sendmsg+0xe8d/0x1370 net/can/j1939/socket.c:1280
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg net/socket.c:744 [inline]
 ____sys_sendmsg+0xab2/0xc90 net/socket.c:2602
 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2656
 __sys_sendmsg+0x117/0x1f0 net/socket.c:2685
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb84577dff9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fb8465c2038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb845935f80 RCX: 00007fb84577dff9
RDX: 0000000000000000 RSI: 0000000020000180 RDI: 0000000000000004
RBP: 00007fb8457f0296 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fb845935f80 R15: 00007ffe38170698
 </TASK>