------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 6503 at lib/refcount.c:28 refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 Modules linked in: CPU: 1 UID: 0 PID: 6503 Comm: kworker/1:4 Not tainted 6.12.0-rc1-syzkaller-g80cb3fb61135 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Workqueue: events nsim_fib_event_work pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 lr : refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 sp : ffff8000800176f0 x29: ffff8000800176f0 x28: dfff800000000000 x27: ffff0000e29c6d64 x26: ffff0000e29c6c80 x25: 00000000000006f9 x24: 0000000000000000 x23: ffff0000e29c6d64 x22: ffff80008a586bd8 x21: 0000000000000003 x20: ffff0000e29c6d64 x19: ffff800092a80000 x18: 0000000000000008 x17: 0000000000000000 x16: ffff8000830b4c50 x15: 0000000000000001 x14: 1fffe000366cc0e2 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000103 x10: 0000000000ff0100 x9 : c8794cb4d5e44700 x8 : c8794cb4d5e44700 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff800080016e18 x4 : ffff80008f8dcac0 x3 : ffff800080626e34 x2 : 0000000000000001 x1 : 0000000000000101 x0 : 0000000000000000 Call trace: refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 __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+0x210/0x43c net/core/skbuff.c:1241 kfree_skb_reason include/linux/skbuff.h:1262 [inline] kfree_skb include/linux/skbuff.h:1271 [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+0x464/0xafc net/can/j1939/transport.c:1484 j1939_tp_cmd_recv net/can/j1939/transport.c:2089 [inline] j1939_tp_recv+0x730/0xe14 net/can/j1939/transport.c:2161 j1939_can_recv+0x5bc/0x934 net/can/j1939/main.c:108 deliver net/can/af_can.c:572 [inline] can_rcv_filter+0x308/0x714 net/can/af_can.c:606 can_receive+0x328/0x488 net/can/af_can.c:663 can_rcv+0x128/0x240 net/can/af_can.c:687 __netif_receive_skb_one_core net/core/dev.c:5662 [inline] __netif_receive_skb+0x18c/0x3c8 net/core/dev.c:5775 process_backlog+0x640/0x123c net/core/dev.c:6107 __napi_poll+0xb4/0x3fc net/core/dev.c:6771 napi_poll net/core/dev.c:6840 [inline] net_rx_action+0x6a8/0xf4c net/core/dev.c:6962 handle_softirqs+0x2e0/0xbf8 kernel/softirq.c:554 __do_softirq+0x14/0x20 kernel/softirq.c:588 ____do_softirq+0x14/0x20 arch/arm64/kernel/irq.c:81 call_on_irq_stack+0x24/0x4c arch/arm64/kernel/entry.S:889 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:86 invoke_softirq kernel/softirq.c:435 [inline] __irq_exit_rcu+0x1d8/0x434 kernel/softirq.c:637 irq_exit_rcu+0x14/0x84 kernel/softirq.c:649 __el1_irq arch/arm64/kernel/entry-common.c:549 [inline] el1_interrupt+0x38/0x68 arch/arm64/kernel/entry-common.c:563 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:568 el1h_64_irq+0x64/0x68 arch/arm64/kernel/entry.S:594 __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] _raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:194 debug_object_free+0x2a0/0x448 lib/debugobjects.c:865 destroy_timer_on_stack kernel/time/timer.c:866 [inline] schedule_timeout+0x1e8/0x33c kernel/time/timer.c:2619 schedule_timeout_uninterruptible+0x74/0xac kernel/time/timer.c:2649 msleep+0x3c/0x68 kernel/time/timer.c:2770 nsim_fib4_rt_add drivers/net/netdevsim/fib.c:369 [inline] nsim_fib4_rt_insert drivers/net/netdevsim/fib.c:432 [inline] nsim_fib4_event drivers/net/netdevsim/fib.c:464 [inline] nsim_fib_event drivers/net/netdevsim/fib.c:884 [inline] nsim_fib_event_work+0x18f0/0x32bc drivers/net/netdevsim/fib.c:1491 process_one_work+0x7bc/0x1600 kernel/workqueue.c:3229 process_scheduled_works kernel/workqueue.c:3310 [inline] worker_thread+0x97c/0xeec kernel/workqueue.c:3391 kthread+0x288/0x310 kernel/kthread.c:389 ret_from_fork+0x10/0x20 arch/arm64/kernel/entry.S:860 irq event stamp: 788225 hardirqs last enabled at (788224): [] __up_console_sem kernel/printk/printk.c:344 [inline] hardirqs last enabled at (788224): [] __console_unlock+0x70/0xc4 kernel/printk/printk.c:2844 hardirqs last disabled at (788225): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:479 softirqs last enabled at (785978): [] spin_unlock_bh include/linux/spinlock.h:396 [inline] softirqs last enabled at (785978): [] nsim_fib_event_work+0x260/0x32bc drivers/net/netdevsim/fib.c:1486 softirqs last disabled at (788183): [] __do_softirq+0x14/0x20 kernel/softirq.c:588 ---[ end trace 0000000000000000 ]---