------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 5930 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
Modules linked in:
CPU: 1 UID: 0 PID: 5930 Comm: syz.3.10 Not tainted 6.13.0-rc1-syzkaller-00025-gfeffde684ac2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024
RIP: 0010:refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
Code: a0 4b 5e 8c e8 c7 43 9e fc 90 0f 0b 90 90 eb 99 e8 fb 9c dd fc c6 05 c0 87 40 0b 01 90 48 c7 c7 00 4c 5e 8c e8 a7 43 9e fc 90 <0f> 0b 90 90 e9 76 ff ff ff e8 d8 9c dd fc c6 05 9a 87 40 0b 01 90
RSP: 0018:ffffc90000a18680 EFLAGS: 00010246
RAX: 3a3c0809ac1fd800 RBX: ffff8880119ad9a4 RCX: ffff88803068da00
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff81601b22 R09: 1ffff110170e519a
R10: dffffc0000000000 R11: ffffed10170e519b R12: ffff8880227f1068
R13: ffff8880119ad9a4 R14: 1ffff110044fe218 R15: ffff8880227f1000
FS:  00007f8a2ed106c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000002000b038 CR3: 0000000030d4e000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <IRQ>
 kfree_skb_reason include/linux/skbuff.h:1263 [inline]
 kfree_skb include/linux/skbuff.h:1272 [inline]
 j1939_session_destroy net/can/j1939/transport.c:282 [inline]
 __j1939_session_release net/can/j1939/transport.c:294 [inline]
 kref_put include/linux/kref.h:65 [inline]
 j1939_session_put+0x1ed/0x440 net/can/j1939/transport.c:299
 j1939_tp_cmd_recv net/can/j1939/transport.c:2113 [inline]
 j1939_tp_recv+0x7fe/0x1050 net/can/j1939/transport.c:2161
 j1939_can_recv+0x732/0xb20 net/can/j1939/main.c:108
 deliver net/can/af_can.c:573 [inline]
 can_rcv_filter+0x359/0x7f0 net/can/af_can.c:607
 can_receive+0x327/0x480 net/can/af_can.c:664
 can_rcv+0x144/0x260 net/can/af_can.c:688
 __netif_receive_skb_one_core net/core/dev.c:5672 [inline]
 __netif_receive_skb+0x2e0/0x650 net/core/dev.c:5785
 process_backlog+0x662/0x15b0 net/core/dev.c:6117
 __napi_poll+0xcb/0x490 net/core/dev.c:6877
 napi_poll net/core/dev.c:6946 [inline]
 net_rx_action+0x89b/0x1240 net/core/dev.c:7068
 handle_softirqs+0x2d4/0x9b0 kernel/softirq.c:554
 __do_softirq kernel/softirq.c:588 [inline]
 invoke_softirq kernel/softirq.c:428 [inline]
 __irq_exit_rcu+0xf7/0x220 kernel/softirq.c:655
 irq_exit_rcu+0x9/0x30 kernel/softirq.c:671
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1049 [inline]
 sysvec_apic_timer_interrupt+0xa6/0xc0 arch/x86/kernel/apic/apic.c:1049
 </IRQ>
 <TASK>
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:152 [inline]
RIP: 0010:_raw_spin_unlock_irqrestore+0xd8/0x140 kernel/locking/spinlock.c:194
Code: 9c 8f 44 24 20 42 80 3c 23 00 74 08 4c 89 f7 e8 5e 9e 3c f6 f6 44 24 21 02 75 52 41 f7 c7 00 02 00 00 74 01 fb bf 01 00 00 00 <e8> 43 f4 a2 f5 65 8b 05 f4 44 39 74 85 c0 74 43 48 c7 04 24 0e 36
RSP: 0018:ffffc9000455f620 EFLAGS: 00000206
RAX: 3a3c0809ac1fd800 RBX: 1ffff920008abec8 RCX: ffffffff817b241a
RDX: dffffc0000000000 RSI: ffffffff8c0a9680 RDI: 0000000000000001
RBP: ffffc9000455f6b0 R08: ffffffff94282997 R09: 1ffffffff2850532
R10: dffffc0000000000 R11: fffffbfff2850533 R12: dffffc0000000000
R13: 1ffff920008abec4 R14: ffffc9000455f640 R15: 0000000000000246
 j1939_sk_send_loop net/can/j1939/socket.c:1164 [inline]
 j1939_sk_sendmsg+0xe01/0x14c0 net/can/j1939/socket.c:1277
 sock_sendmsg_nosec net/socket.c:711 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:726
 ____sys_sendmsg+0x52a/0x7e0 net/socket.c:2583
 ___sys_sendmsg net/socket.c:2637 [inline]
 __sys_sendmmsg+0x36a/0x720 net/socket.c:2726
 __do_sys_sendmmsg net/socket.c:2753 [inline]
 __se_sys_sendmmsg net/socket.c:2750 [inline]
 __x64_sys_sendmmsg+0xa0/0xb0 net/socket.c:2750
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f8a2df7ff19
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:00007f8a2ed10058 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007f8a2e145fa0 RCX: 00007f8a2df7ff19
RDX: 03ffffffffffff06 RSI: 00000000200038c0 RDI: 0000000000000007
RBP: 00007f8a2dff3986 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f8a2e145fa0 R15: 00007ffda73ee208
 </TASK>
----------------
Code disassembly (best guess):
   0:	9c                   	pushf
   1:	8f 44 24 20          	pop    0x20(%rsp)
   5:	42 80 3c 23 00       	cmpb   $0x0,(%rbx,%r12,1)
   a:	74 08                	je     0x14
   c:	4c 89 f7             	mov    %r14,%rdi
   f:	e8 5e 9e 3c f6       	call   0xf63c9e72
  14:	f6 44 24 21 02       	testb  $0x2,0x21(%rsp)
  19:	75 52                	jne    0x6d
  1b:	41 f7 c7 00 02 00 00 	test   $0x200,%r15d
  22:	74 01                	je     0x25
  24:	fb                   	sti
  25:	bf 01 00 00 00       	mov    $0x1,%edi
* 2a:	e8 43 f4 a2 f5       	call   0xf5a2f472 <-- trapping instruction
  2f:	65 8b 05 f4 44 39 74 	mov    %gs:0x743944f4(%rip),%eax        # 0x7439452a
  36:	85 c0                	test   %eax,%eax
  38:	74 43                	je     0x7d
  3a:	48                   	rex.W
  3b:	c7                   	.byte 0xc7
  3c:	04 24                	add    $0x24,%al
  3e:	0e                   	(bad)
  3f:	36                   	ss