------------[ cut here ]------------
WARNING: CPU: 0 PID: 10331 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: 0 PID: 10331 Comm: syz-executor6 Not tainted 4.9.111-g03c70fe #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801a55c74f0 ffffffff81eb2729 ffffffff83c48980 00000000ffffffff
 0000000000000000 0000000000000000 0000000000000107 ffff8801a55c75b0
 ffffffff814219f5 0000000041b58ab3 ffffffff843ba8c0 ffffffff81421836
Call Trace:
 [<ffffffff81eb2729>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb2729>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff814219f5>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81421ce1>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff81136672>] warn_slowpath_fmt+0xc2/0x100 kernel/panic.c:565
 [<ffffffff81f1ac21>] debug_print_object+0x181/0x210 lib/debugobjects.c:260
 [<ffffffff81f1d58b>] __debug_check_no_obj_freed lib/debugobjects.c:720 [inline]
 [<ffffffff81f1d58b>] debug_check_no_obj_freed+0x4fb/0x930 lib/debugobjects.c:749
 [<ffffffff815389dd>] slab_free_hook mm/slub.c:1348 [inline]
 [<ffffffff815389dd>] slab_free_freelist_hook mm/slub.c:1377 [inline]
 [<ffffffff815389dd>] slab_free mm/slub.c:2958 [inline]
 [<ffffffff815389dd>] kfree+0x18d/0x310 mm/slub.c:3878
 [<ffffffff839c1f88>] p9_fd_close+0x298/0x330 net/9p/trans_fd.c:890
 [<ffffffff839b33c5>] p9_client_create+0x825/0x10a0 net/9p/client.c:1050
 [<ffffffff8195ab03>] v9fs_session_init+0x333/0x13a0 fs/9p/v9fs.c:343
 [<ffffffff8194c3fd>] v9fs_mount+0x7d/0x810 fs/9p/vfs_super.c:130
 [<ffffffff8157e22c>] mount_fs+0x28c/0x370 fs/super.c:1206
 [<ffffffff815dd9f1>] vfs_kern_mount.part.29+0xd1/0x3d0 fs/namespace.c:991
 [<ffffffff815e5319>] vfs_kern_mount fs/namespace.c:973 [inline]
 [<ffffffff815e5319>] do_new_mount fs/namespace.c:2513 [inline]
 [<ffffffff815e5319>] do_mount+0x3c9/0x2740 fs/namespace.c:2835
 [<ffffffff8168c3ec>] C_SYSC_mount fs/compat.c:810 [inline]
 [<ffffffff8168c3ec>] compat_SyS_mount+0x4fc/0xff0 fs/compat.c:775
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff839fa3d0>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137
Shutting down cpus with NMI
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..