------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 0 PID: 7851 at lib/refcount.c:28 refcount_warn_saturate+0x1c8/0x20c lib/refcount.c:28 Modules linked in: CPU: 0 UID: 0 PID: 7851 Comm: syz.3.325 Not tainted 6.12.0-rc1-syzkaller-g80cb3fb61135 #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024 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 : ffff8000800076f0 x29: ffff8000800076f0 x28: 0000000000000001 x27: 00000000ffffffff x26: 1fffe0001d987698 x25: dfff800000000000 x24: 0000000000000000 x23: ffff0000e1cc6864 x22: ffff80008a57ce90 x21: 0000000000000003 x20: ffff0000e1cc6864 x19: ffff800092a80000 x18: 0000000000000008 x17: 0000000000000000 x16: ffff8000830b4c50 x15: 0000000000000001 x14: 1fffe000366c78e2 x13: 0000000000000000 x12: 0000000000000000 x11: 0000000000000102 x10: 0000000000ff0100 x9 : de0e8a28e84d1800 x8 : de0e8a28e84d1800 x7 : 0000000000000001 x6 : 0000000000000001 x5 : ffff800080006e18 x4 : ffff80008f8dcac0 x3 : ffff800080626e34 x2 : 0000000000000001 x1 : 0000000100000100 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_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: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 j1939_sk_sendmsg+0xef4/0x10d0 net/can/j1939/socket.c:1280 sock_sendmsg_nosec net/socket.c:729 [inline] __sock_sendmsg net/socket.c:744 [inline] ____sys_sendmsg+0x56c/0x840 net/socket.c:2602 ___sys_sendmsg net/socket.c:2656 [inline] __sys_sendmsg+0x26c/0x33c net/socket.c:2685 __do_sys_sendmsg net/socket.c:2694 [inline] __se_sys_sendmsg net/socket.c:2692 [inline] __arm64_sys_sendmsg+0x80/0x94 net/socket.c:2692 __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:732 el0t_64_sync_handler+0x84/0x108 arch/arm64/kernel/entry-common.c:750 el0t_64_sync+0x190/0x194 arch/arm64/kernel/entry.S:598 irq event stamp: 671 hardirqs last enabled at (670): [] __up_console_sem kernel/printk/printk.c:344 [inline] hardirqs last enabled at (670): [] __console_unlock+0x70/0xc4 kernel/printk/printk.c:2844 hardirqs last disabled at (671): [] el1_dbg+0x24/0x80 arch/arm64/kernel/entry-common.c:479 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 ]---