------------[ cut here ]------------
refcount_t: underflow; use-after-free.
WARNING: CPU: 0 PID: 991 at lib/refcount.c:28 refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Modules linked in:
CPU: 0 PID: 991 Comm: kworker/u4:4 Not tainted 5.16.0-syzkaller-11655-ge5313968c41b #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net

RIP: 0010:refcount_warn_saturate+0x1d1/0x1e0 lib/refcount.c:28
Code: e9 db fe ff ff 48 89 df e8 5c c9 e1 fd e9 8a fe ff ff e8 c2 22 9a fd 48 c7 c7 00 c5 05 8a c6 05 0d d1 a0 09 01 e8 b1 bb 27 05 <0f> 0b e9 af fe ff ff 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55
RSP: 0018:ffffc90004e97950 EFLAGS: 00010286

RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff88801c483a00 RSI: ffffffff815fa058 RDI: fffff520009d2f1c
RBP: 0000000000000003 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815f3dbe R11: 0000000000000000 R12: ffffe8ffffd2d115
R13: 0000000000000000 R14: 0000000000000007 R15: ffffe8ffffd2d039
FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5d5ea82718 CR3: 00000000133c9000 CR4: 00000000003506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
 __refcount_sub_and_test include/linux/refcount.h:283 [inline]
 __refcount_dec_and_test include/linux/refcount.h:315 [inline]
 refcount_dec_and_test include/linux/refcount.h:333 [inline]
 skb_unref include/linux/skbuff.h:1101 [inline]
 skb_unref include/linux/skbuff.h:1095 [inline]
 kfree_skb_reason+0x330/0x400 net/core/skbuff.c:772
 kfree_skb include/linux/skbuff.h:1115 [inline]
 flush_gro_hash net/core/dev.c:6326 [inline]
 __netif_napi_del.part.0+0x2ca/0x530 net/core/dev.c:6341
 __netif_napi_del+0x3c/0x50 net/core/dev.c:6334
 gro_cells_destroy net/core/gro_cells.c:102 [inline]
 gro_cells_destroy+0x115/0x360 net/core/gro_cells.c:92
 ip_tunnel_dev_free+0x15/0x60 net/ipv4/ip_tunnel.c:1010
 netdev_run_todo+0x6c3/0xaa0 net/core/dev.c:9962
 ip_tunnel_delete_nets+0x3a4/0x5b0 net/ipv4/ip_tunnel.c:1124
 ops_exit_list+0x125/0x170 net/core/net_namespace.c:173
 cleanup_net+0x4ea/0xb00 net/core/net_namespace.c:598
 process_one_work+0x9ac/0x1650 kernel/workqueue.c:2307
 worker_thread+0x657/0x1110 kernel/workqueue.c:2454
 kthread+0x2e9/0x3a0 kernel/kthread.c:377
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295
 </TASK>