------------[ cut here ]------------ refcount_t: underflow; use-after-free. WARNING: CPU: 2 PID: 5405 at lib/refcount.c:28 refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28 Modules linked in: CPU: 2 UID: 0 PID: 5405 Comm: syz.2.3 Not tainted 6.12.0-rc1-syzkaller-00306-g27cc6fdf7201 #0 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2~bpo12+1 04/01/2014 RIP: 0010:refcount_warn_saturate+0x14a/0x210 lib/refcount.c:28 Code: ff 89 de e8 78 21 fe fc 84 db 0f 85 66 ff ff ff e8 8b 1f fe fc c6 05 c1 94 b8 0b 01 90 48 c7 c7 40 4b d1 8b e8 37 0e bf fc 90 <0f> 0b 90 90 e9 43 ff ff ff e8 68 1f fe fc 0f b6 1d 9c 94 b8 0b 31 RSP: 0018:ffffc9000322ee68 EFLAGS: 00010286 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffc9000c001000 RDX: 0000000000040000 RSI: ffffffff814e71b6 RDI: 0000000000000001 RBP: ffff88802168dda4 R08: 0000000000000001 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000002 R13: 0000000000000000 R14: ffff88802168dda4 R15: 0000000000000001 FS: 00007f1f421796c0(0000) GS:ffff88806a800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007ff231453ef0 CR3: 000000001f976000 CR4: 0000000000352ef0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __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+0x183/0x1a0 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+0x163/0x460 net/can/j1939/transport.c:282 __j1939_session_release net/can/j1939/transport.c:294 [inline] kref_put include/linux/kref.h:65 [inline] j1939_session_put net/can/j1939/transport.c:299 [inline] j1939_session_deactivate_locked+0x275/0x320 net/can/j1939/transport.c:1086 j1939_cancel_active_session+0x183/0x350 net/can/j1939/transport.c:2211 j1939_netdev_notify+0x19e/0x1e0 net/can/j1939/main.c:376 notifier_call_chain+0xb9/0x410 kernel/notifier.c:93 call_netdevice_notifiers_info+0xbe/0x140 net/core/dev.c:1996 call_netdevice_notifiers_extack net/core/dev.c:2034 [inline] call_netdevice_notifiers net/core/dev.c:2048 [inline] dev_close_many+0x333/0x6a0 net/core/dev.c:1589 unregister_netdevice_many_notify+0x489/0x1e50 net/core/dev.c:11377 rtnl_delete_link net/core/rtnetlink.c:3252 [inline] rtnl_dellink+0x3c9/0xae0 net/core/rtnetlink.c:3304 rtnetlink_rcv_msg+0x3c7/0xea0 net/core/rtnetlink.c:6646 netlink_rcv_skb+0x16b/0x440 net/netlink/af_netlink.c:2550 netlink_unicast_kernel net/netlink/af_netlink.c:1331 [inline] netlink_unicast+0x53c/0x7f0 net/netlink/af_netlink.c:1357 netlink_sendmsg+0x8b8/0xd70 net/netlink/af_netlink.c:1901 sock_sendmsg_nosec net/socket.c:729 [inline] __sock_sendmsg net/socket.c:744 [inline] ____sys_sendmsg+0xaaf/0xc90 net/socket.c:2602 ___sys_sendmsg+0x135/0x1e0 net/socket.c:2656 __sys_sendmsg+0x117/0x1f0 net/socket.c:2685 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0xcd/0x250 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x77/0x7f RIP: 0033:0x7f1f4137dff9 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:00007f1f42179038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e RAX: ffffffffffffffda RBX: 00007f1f41535f80 RCX: 00007f1f4137dff9 RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000008 RBP: 00007f1f413f0296 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000 R13: 0000000000000000 R14: 00007f1f41535f80 R15: 00007fff87fcc648