------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 1 PID: 6535 at lib/refcount.c:28 refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 Modules linked in: CPU: 1 UID: 0 PID: 6535 Comm: syz.0.10 Not tainted 6.12.0-syzkaller-g7b1d1d4cfac0 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/13/2024 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: 0000000000000001 x27: 00000000ffffffff x26: 1fffe0001ae77418 x25: dfff800000000000 x24: 0000000000000000 x23: ffff0000c7102ea4 x22: ffff80008a63b670 x21: 0000000000000003 x20: ffff0000c7102ea4 x19: ffff800092b74000 x18: 0000000000000008 x17: 0000000000000000 x16: ffff8000831615b0 x15: 0000000000000001 x14: 1fffe000366c80e2 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000103 x10: 0000000000ff0100 x9 : f54a0ea1699caa00 x8 : f54a0ea1699caa00 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff800080016e18 x4 : ffff80008f9bd220 x3 : ffff800080626d8c x2 : 0000000000000001 x1 : 0000000100000101 x0 : 0000000000000000 Call trace: refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 (P) refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 (L) __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_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+0x1c8/0x460 net/can/j1939/transport.c:299 j1939_xtp_rx_eoma+0x2d0/0x4c0 net/can/j1939/transport.c:1411 j1939_tp_cmd_recv net/can/j1939/transport.c:2113 [inline] j1939_tp_recv+0x698/0xe14 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:5670 [inline] __netif_receive_skb+0x18c/0x3c8 net/core/dev.c:5783 process_backlog+0x640/0x123c net/core/dev.c:6115 __napi_poll+0xb4/0x3fc net/core/dev.c:6779 napi_poll net/core/dev.c:6848 [inline] net_rx_action+0x6a8/0xf4c net/core/dev.c:6970 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:891 do_softirq_own_stack+0x20/0x2c arch/arm64/kernel/irq.c:86 invoke_softirq kernel/softirq.c:435 [inline] __irq_exit_rcu+0x1d8/0x544 kernel/softirq.c:655 irq_exit_rcu+0x14/0x84 kernel/softirq.c:671 __el1_irq arch/arm64/kernel/entry-common.c:561 [inline] el1_interrupt+0x38/0x68 arch/arm64/kernel/entry-common.c:575 el1h_64_irq_handler+0x18/0x24 arch/arm64/kernel/entry-common.c:580 el1h_64_irq+0x6c/0x70 arch/arm64/kernel/entry.S:596 __daif_local_irq_restore arch/arm64/include/asm/irqflags.h:175 [inline] (P) arch_local_irq_restore arch/arm64/include/asm/irqflags.h:195 [inline] (P) __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] (P) _raw_spin_unlock_irqrestore+0x44/0x98 kernel/locking/spinlock.c:194 (P) __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:151 [inline] (L) _raw_spin_unlock_irqrestore+0x38/0x98 kernel/locking/spinlock.c:194 (L) unlock_hrtimer_base kernel/time/hrtimer.c:1016 [inline] hrtimer_start_range_ns+0x8bc/0x9e0 kernel/time/hrtimer.c:1305 hrtimer_start include/linux/hrtimer.h:275 [inline] j1939_tp_schedule_txtimer+0x88/0xdc net/can/j1939/transport.c:702 j1939_sk_send_loop net/can/j1939/socket.c:1164 [inline] j1939_sk_sendmsg+0xb00/0x10d0 net/can/j1939/socket.c:1277 sock_sendmsg_nosec net/socket.c:729 [inline] __sock_sendmsg net/socket.c:744 [inline] ____sys_sendmsg+0x56c/0x840 net/socket.c:2607 ___sys_sendmsg net/socket.c:2661 [inline] __sys_sendmmsg+0x318/0x7e0 net/socket.c:2747 __do_sys_sendmmsg net/socket.c:2776 [inline] __se_sys_sendmmsg net/socket.c:2773 [inline] __arm64_sys_sendmmsg+0xa0/0xbc net/socket.c:2773 __invoke_syscall arch/arm64/kernel/syscall.c:35 [inline] invoke_syscall+0x98/0x2b8 arch/arm64/kernel/syscall.c:49 el0_svc_common+0x130/0x23c arch/arm64/kernel/syscall.c:132 do_el0_svc+0x48/0x58 arch/arm64/kernel/syscall.c:151 el0_svc+0x54/0x168 arch/arm64/kernel/entry-common.c:744 el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:762 el0t_64_sync+0x198/0x19c arch/arm64/kernel/entry.S:600 irq event stamp: 659 hardirqs last enabled at (658): [] __up_console_sem kernel/printk/printk.c:344 [inline] hardirqs last enabled at (658): [] __console_unlock+0x70/0xc4 kernel/printk/printk.c:2844 hardirqs last disabled at (659): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:488 softirqs last enabled at (248): [] spin_unlock_bh include/linux/spinlock.h:396 [inline] softirqs last enabled at (248): [] j1939_session_list_unlock net/can/j1939/transport.c:243 [inline] softirqs last enabled at (248): [] j1939_session_activate+0x238/0x378 net/can/j1939/transport.c:1583 softirqs last disabled at (253): [] __do_softirq+0x14/0x20 kernel/softirq.c:588 ---[ end trace 0000000000000000 ]---