------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 3 PID: 8599 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Modules linked in:
CPU: 3 UID: 0 PID: 8599 Comm: syz.3.812 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 38 49 03 fd 84 db 0f 85 66 ff ff ff e8 4b 47 03 fd c6 05 63 4d 7c 0b 01 90 48 c7 c7 a0 e5 b0 8b e8 a7 c4 c4 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 28 47 03 fd 0f b6 1d 3e 4d 7c 0b 31
RSP: 0018:ffffc90002f9f918 EFLAGS: 00010282
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
CR2: 00000000f7445008 CR3: 000000004f87c000 CR4: 0000000000352ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __sys_sendmsg+0x117/0x1f0 net/socket.c:2690
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Kernel panic - not syncing: kernel: panic_on_warn set ...
CPU: 3 UID: 0 PID: 8599 Comm: syz.3.812 Not tainted 6.12.0-rc5-syzkaller-00044-gc1e939a21eb1 #0
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:94 [inline]
 dump_stack_lvl+0x3d/0x1f0 lib/dump_stack.c:120
 panic+0x71d/0x800 kernel/panic.c:354
 check_panic_on_warn+0xab/0xb0 kernel/panic.c:243
 __warn+0xf6/0x3d0 kernel/panic.c:748
 __report_bug lib/bug.c:199 [inline]
 report_bug+0x3c0/0x580 lib/bug.c:219
 handle_bug+0x54/0xa0 arch/x86/kernel/traps.c:285
 exc_invalid_op+0x17/0x50 arch/x86/kernel/traps.c:309
 asm_exc_invalid_op+0x1a/0x20 arch/x86/include/asm/idtentry.h:621
RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28
Code: ff 89 de e8 38 49 03 fd 84 db 0f 85 66 ff ff ff e8 4b 47 03 fd c6 05 63 4d 7c 0b 01 90 48 c7 c7 a0 e5 b0 8b e8 a7 c4 c4 fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 28 47 03 fd 0f b6 1d 3e 4d 7c 0b 31
RSP: 0018:ffffc90002f9f918 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc90032258000
RDX: 0000000000040000 RSI: ffffffff814e24c6 RDI: 0000000000000001
RBP: ffff8880661fb4e4 R08: 0000000000000001 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002
R13: 0000000000000000 R14: ffff8880661fb4e4 R15: 0000000000000001
 __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+0x64/0x90 net/can/j1939/transport.c:299
 j1939_sk_send_loop net/can/j1939/socket.c:1202 [inline]
 j1939_sk_sendmsg+0xe8f/0x13c0 net/can/j1939/socket.c:1277
 sock_sendmsg_nosec net/socket.c:729 [inline]
 __sock_sendmsg net/socket.c:744 [inline]
 ____sys_sendmsg+0x9ae/0xb40 net/socket.c:2607
 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2661
 __sys_sendmsg+0x117/0x1f0 net/socket.c:2690
 do_syscall_32_irqs_on arch/x86/entry/common.c:165 [inline]
 __do_fast_syscall_32+0x73/0x120 arch/x86/entry/common.c:386
 do_fast_syscall_32+0x32/0x80 arch/x86/entry/common.c:411
 entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7f7f579
Code: b8 01 10 06 03 74 b4 01 10 07 03 74 b0 01 10 08 03 74 d8 01 00 00 00 00 00 00 00 00 00 00 00 00 00 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 8d b4 26 00 00 00 00 8d b4 26 00 00 00 00
RSP: 002b:00000000f570655c EFLAGS: 00000296 ORIG_RAX: 0000000000000172
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000020000180
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000296 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
 </TASK>
Kernel Offset: disabled
----------------
Code disassembly (best guess), 2 bytes skipped:
   0:	10 06                	adc    %al,(%rsi)
   2:	03 74 b4 01          	add    0x1(%rsp,%rsi,4),%esi
   6:	10 07                	adc    %al,(%rdi)
   8:	03 74 b0 01          	add    0x1(%rax,%rsi,4),%esi
   c:	10 08                	adc    %cl,(%rax)
   e:	03 74 d8 01          	add    0x1(%rax,%rbx,8),%esi
  1e:	00 51 52             	add    %dl,0x52(%rcx)
  21:	55                   	push   %rbp
  22:	89 e5                	mov    %esp,%ebp
  24:	0f 34                	sysenter
  26:	cd 80                	int    $0x80
* 28:	5d                   	pop    %rbp <-- trapping instruction
  29:	5a                   	pop    %rdx
  2a:	59                   	pop    %rcx
  2b:	c3                   	ret
  2c:	90                   	nop
  2d:	90                   	nop
  2e:	90                   	nop
  2f:	90                   	nop
  30:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi
  37:	8d b4 26 00 00 00 00 	lea    0x0(%rsi,%riz,1),%esi