------------[ cut here ]------------
virt_to_cache: Object is not a Slab page!
WARNING: CPU: 1 PID: 1161 at mm/slab.h:420 virt_to_cache mm/slab.h:420 [inline]
WARNING: CPU: 1 PID: 1161 at mm/slab.h:420 kfree+0x29b/0x2b0 mm/slab.c:3752
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 1161 Comm: kworker/u4:9 Not tainted 5.9.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x198/0x1fd lib/dump_stack.c:118
 panic+0x382/0x7fb kernel/panic.c:231
 __warn.cold+0x20/0x4b kernel/panic.c:600
 report_bug+0x1bd/0x210 lib/bug.c:198
 handle_bug+0x38/0x90 arch/x86/kernel/traps.c:234
 exc_invalid_op+0x14/0x40 arch/x86/kernel/traps.c:254
 asm_exc_invalid_op+0x12/0x20 arch/x86/include/asm/idtentry.h:536
RIP: 0010:virt_to_cache mm/slab.h:420 [inline]
RIP: 0010:kfree+0x29b/0x2b0 mm/slab.c:3752
Code: 05 91 b6 9d 09 01 e8 29 bf a5 ff e9 7a ff ff ff 48 c7 c6 80 70 96 88 48 c7 c7 70 c9 b2 89 c6 05 25 db 9d 09 01 e8 67 dd 8f ff <0f> 0b e9 bf fe ff ff 0f 0b 66 90 66 2e 0f 1f 84 00 00 00 00 00 41
RSP: 0018:ffffc90016137b50 EFLAGS: 00010086
RAX: 0000000000000000 RBX: 0000000000000286 RCX: 0000000000000000
RDX: ffff888061194000 RSI: ffffffff815f59d5 RDI: fffff52002c26f5c
RBP: ffff888000400000 R08: 0000000000000001 R09: ffff8880ae520f8b
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000200
R13: 000000000002bfa8 R14: ffff888000400000 R15: 0000000000000800
 kvfree+0x42/0x50 mm/util.c:603
 nfsd_reply_cache_shutdown+0x1a3/0x2c0 fs/nfsd/nfscache.c:214
 nfsd_exit_net+0x15f/0x490 fs/nfsd/nfsctl.c:1507
 ops_exit_list+0xb0/0x160 net/core/net_namespace.c:186
 cleanup_net+0x4ea/0xa00 net/core/net_namespace.c:603
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294
Kernel Offset: disabled
Rebooting in 86400 seconds..