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WARNING: CPU: 1 PID: 5816 at kernel/nstree.c:189 __ns_tree_add_raw+0xa92/0xb30
Modules linked in:
CPU: 1 UID: 0 PID: 5816 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
RIP: 0010:__ns_tree_add_raw+0xa92/0xb30
Code: 32 00 90 0f 0b 90 42 80 3c 23 00 0f 85 1e fc ff ff e9 21 fc ff ff e8 ed 78 32 00 90 0f 0b 90 e9 66 fc ff ff e8 df 78 32 00 90 <0f> 0b 90 e9 53 ff ff ff 44 89 f9 80 e1 07 80 c1 03 38 c1 0f 8c ef
RSP: 0018:ffffc90003f27c30 EFLAGS: 00010293
RAX: ffffffff818e0051 RBX: 1ffffffff16db871 RCX: ffff88810ffe0000
RDX: 0000000000000000 RSI: ffff8881bbf5e9a8 RDI: ffff88816d0e6e00
RBP: ffff88816d0e6e00 R08: ffff88816d0e6e3f R09: 0000000000000000
R10: ffff88816d0e6e30 R11: ffffffff81b988c0 R12: dffffc0000000000
R13: ffff88816d0e6e40 R14: ffffffff8b6dc388 R15: ffff8881bbf5e9a8
FS:  000055558630f500(0000) GS:ffff8882a9d04000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f5c3f03529c CR3: 000000010b5bc000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 copy_cgroup_ns+0x373/0x5f0
 create_new_namespaces+0x358/0x720
 unshare_nsproxy_namespaces+0x11c/0x170
 ksys_unshare+0x4c8/0x8c0
 __x64_sys_unshare+0x38/0x50
 do_syscall_64+0xfa/0xfa0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f5c3ef907c7
Code: 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48 83 c8 ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 10 01 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffc62c39c88 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007ffc62c39c90 RCX: 00007f5c3ef907c7
RDX: 0000000000000000 RSI: 00007f5c3f03529c RDI: 0000000002000000
RBP: 00007ffc62c39d20 R08: 0000000000000000 R09: 00007f5c3fd1d6c0
R10: 0000000000044000 R11: 0000000000000246 R12: 00007ffc62c39d20
R13: 00007ffc62c39d28 R14: 0000000000000009 R15: 0000000000000000
 </TASK>