------------[ cut here ]------------
dst_release underflow
WARNING: CPU: 0 PID: 9 at net/core/dst.c:175 dst_release net/core/dst.c:175 [inline]
WARNING: CPU: 0 PID: 9 at net/core/dst.c:175 dst_release+0xd2/0xe0 net/core/dst.c:169
Modules linked in:
CPU: 0 PID: 9 Comm: kworker/u4:0 Not tainted 5.12.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
RIP: 0010:dst_release net/core/dst.c:175 [inline]
RIP: 0010:dst_release+0xd2/0xe0 net/core/dst.c:169
Code: 89 c3 89 c6 e8 0f 7e 71 fa 85 db 74 a4 e9 63 35 02 02 e8 51 76 71 fa 48 c7 c7 c0 ab 66 8a c6 05 bc 57 af 06 01 e8 67 08 c6 01 <0f> 0b eb c6 66 2e 0f 1f 84 00 00 00 00 00 41 56 41 55 41 54 55 48
RSP: 0018:ffffc90000ce79e8 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 0000000000000000
RDX: ffff888011570000 RSI: ffffffff815c5205 RDI: fffff5200019cf2f
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: ffffffff815bdf9e R11: 0000000000000000 R12: ffff88801da876c0
R13: 00000000ffffffff R14: fffffbfff1b8c2b4 R15: 0000000000000000
FS:  0000000000000000(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f1aa35c0000 CR3: 000000006921c000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 dst_cache_destroy net/core/dst_cache.c:160 [inline]
 dst_cache_destroy+0xd4/0x1d0 net/core/dst_cache.c:152
 ip_tunnel_dev_free+0x21/0x60 net/ipv4/ip_tunnel.c:1001
 netdev_run_todo+0x6b4/0xa80 net/core/dev.c:10556
 ip_tunnel_delete_nets+0x3f0/0x5b0 net/ipv4/ip_tunnel.c:1114
 ops_exit_list+0x10d/0x160 net/core/net_namespace.c:178
 cleanup_net+0x4ea/0xb10 net/core/net_namespace.c:595
 process_one_work+0x98d/0x1600 kernel/workqueue.c:2275
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2421
 kthread+0x3b1/0x4a0 kernel/kthread.c:292
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294