------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 1 PID: 5945 at lib/refcount.c:28 refcount_warn_saturate+0x15a/0x1d0 lib/refcount.c:28
Modules linked in:
CPU: 1 UID: 0 PID: 5945 Comm: syz.3.13 Not tainted 6.12.0-next-20241126-syzkaller #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: e0 44 5f 8c e8 77 bc 93 fc 90 0f 0b 90 90 eb 99 e8 db 1d d3 fc c6 05 36 68 37 0b 01 90 48 c7 c7 40 45 5f 8c e8 57 bc 93 fc 90 <0f> 0b 90 90 e9 76 ff ff ff e8 b8 1d d3 fc c6 05 10 68 37 0b 01 90
RSP: 0018:ffffc90000a18640 EFLAGS: 00010246
RAX: 61158f57888db300 RBX: ffff88807b684ae4 RCX: ffff8880278f8000
RDX: 0000000000000100 RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000003 R08: ffffffff81602b32 R09: fffffbfff1cfa218
R10: dffffc0000000000 R11: fffffbfff1cfa218 R12: ffff88805e39b800
R13: ffff88807b684ae4 R14: ffff88805e39b800 R15: ffff88805b26cc18
FS: 00007fe6e696f6c0(0000) GS:ffff8880b8700000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000110c35e430 CR3: 00000000294d0000 CR4: 00000000003526f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
kfree_skb_reason include/linux/skbuff.h:1263 [inline]
kfree_skb include/linux/skbuff.h:1272 [inline]
j1939_session_skb_drop_old net/can/j1939/transport.c:347 [inline]
j1939_xtp_rx_cts_one net/can/j1939/transport.c:1445 [inline]
j1939_xtp_rx_cts+0x552/0xc70 net/can/j1939/transport.c:1484
j1939_tp_cmd_recv net/can/j1939/transport.c:2089 [inline]
j1939_tp_recv+0x8ae/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+0x2c5/0x980 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
asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
RIP: 0010:finish_task_switch+0x1ea/0x870 kernel/sched/core.c:5243
Code: c9 50 e8 79 07 0c 00 48 83 c4 08 4c 89 f7 e8 9d 39 00 00 e9 de 04 00 00 4c 89 f7 e8 90 6d 68 0a e8 cb 9f 38 00 fb 48 8b 5d c0 <48> 8d bb f8 15 00 00 48 89 f8 48 c1 e8 03 49 be 00 00 00 00 00 fc
RSP: 0018:ffffc900041ef1a8 EFLAGS: 00000286
RAX: 61158f57888db300 RBX: ffff8880278f8000 RCX: ffffffff9a3cb903
RDX: dffffc0000000000 RSI: ffffffff8c0a9640 RDI: ffffffff8c5f89e0
RBP: ffffc900041ef1f0 R08: ffffffff90199cf7 R09: 1ffffffff203339e
R10: dffffc0000000000 R11: fffffbfff203339f R12: 1ffff110170e7edc
R13: dffffc0000000000 R14: ffff8880b863e8c0 R15: ffff8880b873f6e0
context_switch kernel/sched/core.c:5372 [inline]
__schedule+0x1858/0x4c30 kernel/sched/core.c:6756
__schedule_loop kernel/sched/core.c:6833 [inline]
schedule+0x14b/0x320 kernel/sched/core.c:6848
schedule_timeout+0xb0/0x290 kernel/time/sleep_timeout.c:75
unix_wait_for_peer+0x250/0x340 net/unix/af_unix.c:1529
unix_dgram_sendmsg+0x127f/0x1f80 net/unix/af_unix.c:2131
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: 0033:0x7fe6e5b7e819
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:00007fe6e696f038 EFLAGS: 00000246 ORIG_RAX: 0000000000000133
RAX: ffffffffffffffda RBX: 00007fe6e5d35fa0 RCX: 00007fe6e5b7e819
RDX: 0000000000000651 RSI: 0000000020000000 RDI: 0000000000000004
RBP: 00007fe6e5bf175e R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007fe6e5d35fa0 R15: 00007ffc668d3e78
----------------
Code disassembly (best guess):
0: c9 leave
1: 50 push %rax
2: e8 79 07 0c 00 call 0xc0780
7: 48 83 c4 08 add $0x8,%rsp
b: 4c 89 f7 mov %r14,%rdi
e: e8 9d 39 00 00 call 0x39b0
13: e9 de 04 00 00 jmp 0x4f6
18: 4c 89 f7 mov %r14,%rdi
1b: e8 90 6d 68 0a call 0xa686db0
20: e8 cb 9f 38 00 call 0x389ff0
25: fb sti
26: 48 8b 5d c0 mov -0x40(%rbp),%rbx
* 2a: 48 8d bb f8 15 00 00 lea 0x15f8(%rbx),%rdi <-- trapping instruction
31: 48 89 f8 mov %rdi,%rax
34: 48 c1 e8 03 shr $0x3,%rax
38: 49 rex.WB
39: be 00 00 00 00 mov $0x0,%esi
3e: 00 fc add %bh,%ah