------------[ cut here ]------------
ida_free called for id=1326 which is not allocated.
WARNING: CPU: 0 PID: 6146 at lib/idr.c:592 ida_free+0x280/0x310 lib/idr.c:592
Modules linked in:
CPU: 0 UID: 0 PID: 6146 Comm: syz.1.60 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:ida_free+0x280/0x310 lib/idr.c:592
Code: 00 00 00 00 fc ff df 48 8b 5c 24 10 48 8b 7c 24 40 48 89 de e8 d1 8a 0c 00 90 48 c7 c7 80 ee ba 8c 44 89 fe e8 11 87 12 f6 90 <0f> 0b 90 90 eb 34 e8 95 02 4f f6 49 bd 00 00 00 00 00 fc ff df eb
RSP: 0018:ffffc9000302fba0 EFLAGS: 00010246
RAX: c838d58ce4bb0000 RBX: 0000000000000a06 RCX: ffff88801eac0000
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000002
RBP: ffffc9000302fca0 R08: ffff88804b024293 R09: 1ffff11009604852
R10: dffffc0000000000 R11: ffffed1009604853 R12: 1ffff92000605f78
R13: dffffc0000000000 R14: ffff888026c1fd00 R15: 000000000000052e
FS:  00007f6d7aab16c0(0000) GS:ffff8880b8613000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000200000004000 CR3: 000000002726e000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 copy_net_ns+0x37a/0x510 net/core/net_namespace.c:593
 create_new_namespaces+0x3f3/0x720 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x11c/0x170 kernel/nsproxy.c:218
 ksys_unshare+0x4c8/0x8c0 kernel/fork.c:3127
 __do_sys_unshare kernel/fork.c:3198 [inline]
 __se_sys_unshare kernel/fork.c:3196 [inline]
 __x64_sys_unshare+0x38/0x50 kernel/fork.c:3196
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xfa/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f6d79b8eba9
Code: ff ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 40 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 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:00007f6d7aab1038 EFLAGS: 00000246 ORIG_RAX: 0000000000000110
RAX: ffffffffffffffda RBX: 00007f6d79dd5fa0 RCX: 00007f6d79b8eba9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000062040200
RBP: 00007f6d79c11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f6d79dd6038 R14: 00007f6d79dd5fa0 R15: 00007ffd5ab830f8
 </TASK>