------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 4470 at lib/refcount.c:28 refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 Modules linked in: CPU: 1 UID: 0 PID: 4470 Comm: kworker/u8:8 Not tainted 6.12.0-rc1-syzkaller-g80cb3fb61135 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 Workqueue: bat_events batadv_nc_worker 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: ffff0000d4823224 x26: ffff0000d4823140 x25: 00000000000006f9 x24: 0000000000000000 x23: ffff0000d4823224 x22: ffff80008a586bd8 x21: 0000000000000003 x20: ffff0000d4823224 x19: ffff800092a80000 x18: 0000000000000008 x17: 0000000000000000 x16: ffff80008b3bdbf0 x15: ffff700011f0d488 x14: 1ffff00011f0d488 x13: 0000000000000004 x12: ffffffffffffffff x11: 0000000000000103 x10: 0000000000ff0100 x9 : e442b2cfa3ee6300 x8 : e442b2cfa3ee6300 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff800080016e18 x4 : ffff80008f8dcac0 x3 : ffff80008039400c x2 : 0000000000000000 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 do_softirq+0x90/0xf8 kernel/softirq.c:455 __local_bh_enable_ip+0x288/0x44c kernel/softirq.c:382 __raw_spin_unlock_bh include/linux/spinlock_api_smp.h:167 [inline] _raw_spin_unlock_bh+0x3c/0x4c kernel/locking/spinlock.c:210 spin_unlock_bh include/linux/spinlock.h:396 [inline] batadv_nc_purge_paths+0x2f4/0x378 net/batman-adv/network-coding.c:471 batadv_nc_worker+0x2e4/0x580 net/batman-adv/network-coding.c:720 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: 1126067 hardirqs last enabled at (1126066): [] __up_console_sem kernel/printk/printk.c:344 [inline] hardirqs last enabled at (1126066): [] __console_unlock+0x70/0xc4 kernel/printk/printk.c:2844 hardirqs last disabled at (1126067): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:479 softirqs last enabled at (1118550): [] spin_unlock_bh include/linux/spinlock.h:396 [inline] softirqs last enabled at (1118550): [] batadv_nc_purge_paths+0x2f4/0x378 net/batman-adv/network-coding.c:471 softirqs last disabled at (1118551): [] __do_softirq+0x14/0x20 kernel/softirq.c:588 ---[ end trace 0000000000000000 ]---