------------[ cut here ]------------
WARNING: CPU: 1 PID: 7142 at lib/debugobjects.c:263 debug_print_object+0x181/0x210 lib/debugobjects.c:260
ODEBUG: free active (active state 0) object type: work_struct hint: p9_read_work+0x0/0xac0 include/linux/workqueue.h:535
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 7142 Comm: syz-executor1 Not tainted 4.9.124-g09eb2ba #31
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801ca60f7f0 ffffffff81eb95e9 ffffffff83c48ac0 00000000ffffffff
 0000000000000000 0000000000000001 0000000000000107 ffff8801ca60f8b0
 ffffffff81423eb5 0000000041b58ab3 ffffffff843bb8e8 ffffffff81423cf6
Call Trace:
 [<ffffffff81eb95e9>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb95e9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81423eb5>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff814241a1>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff81138252>] warn_slowpath_fmt+0xc2/0x100 kernel/panic.c:565
 [<ffffffff81f21b01>] debug_print_object+0x181/0x210 lib/debugobjects.c:260
 [<ffffffff81f2446b>] __debug_check_no_obj_freed lib/debugobjects.c:720 [inline]
 [<ffffffff81f2446b>] debug_check_no_obj_freed+0x4fb/0x930 lib/debugobjects.c:749
 [<ffffffff8153c93d>] slab_free_hook mm/slub.c:1348 [inline]
 [<ffffffff8153c93d>] slab_free_freelist_hook mm/slub.c:1377 [inline]
 [<ffffffff8153c93d>] slab_free mm/slub.c:2958 [inline]
 [<ffffffff8153c93d>] kfree+0x18d/0x310 mm/slub.c:3878
 [<ffffffff839cac18>] p9_fd_close+0x298/0x330 net/9p/trans_fd.c:890
 [<ffffffff839b7cf3>] p9_client_destroy+0x73/0x570 net/9p/client.c:1070
 [<ffffffff81961456>] v9fs_session_close+0x46/0x110 fs/9p/v9fs.c:434
 [<ffffffff819513fe>] v9fs_kill_super+0x4e/0xa0 fs/9p/vfs_super.c:226
 [<ffffffff8157ea75>] deactivate_locked_super+0x75/0xd0 fs/super.c:310
 [<ffffffff81951fe6>] v9fs_mount+0x3c6/0x810 fs/9p/vfs_super.c:207
 [<ffffffff81582a3c>] mount_fs+0x28c/0x370 fs/super.c:1206
 [<ffffffff815e2321>] vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:1000
 [<ffffffff815e9b49>] vfs_kern_mount fs/namespace.c:982 [inline]
 [<ffffffff815e9b49>] do_new_mount fs/namespace.c:2537 [inline]
 [<ffffffff815e9b49>] do_mount+0x3c9/0x2740 fs/namespace.c:2859
 [<ffffffff815ec89e>] SYSC_mount fs/namespace.c:3075 [inline]
 [<ffffffff815ec89e>] SyS_mount+0xfe/0x110 fs/namespace.c:3052
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a019d3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Shutting down cpus with NMI
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..