Re: WARNING in xfrm_policy_fini

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit:    a3b22b9f11d9 Linux 5.0-rc7
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17e3d4d0c00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=7132344728e7ec3f
dashboard link: https://syzkaller.appspot.com/bug?extid=9bce6db6c82f06b85d8b
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=177317a8c00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+9bce6db6c82f06b85d8b@xxxxxxxxxxxxxxxxxxxxxxxxx

bond0 (unregistering): Releasing backup interface bond_slave_1
bond0 (unregistering): Releasing backup interface bond_slave_0
bond0 (unregistering): Released all slaves
cgroup: fork rejected by pids controller in /syz3
cgroup: fork rejected by pids controller in /syz2
WARNING: CPU: 1 PID: 31 at net/xfrm/xfrm_policy.c:3871  
xfrm_policy_fini+0x30c/0x3a0 net/xfrm/xfrm_policy.c:3871
Kernel panic - not syncing: panic_on_warn set ...
CPU: 1 PID: 31 Comm: kworker/u4:2 Not tainted 5.0.0-rc7 #77
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+0x172/0x1f0 lib/dump_stack.c:113
 panic+0x2cb/0x65c kernel/panic.c:214
 __warn.cold+0x20/0x45 kernel/panic.c:571
 report_bug+0x263/0x2b0 lib/bug.c:186
 fixup_bug arch/x86/kernel/traps.c:178 [inline]
 fixup_bug arch/x86/kernel/traps.c:173 [inline]
 do_error_trap+0x11b/0x200 arch/x86/kernel/traps.c:271
 do_invalid_op+0x37/0x50 arch/x86/kernel/traps.c:290
 invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:973
kobject: 'loop1' (00000000fd200829): kobject_uevent_env
RIP: 0010:xfrm_policy_fini+0x30c/0x3a0 net/xfrm/xfrm_policy.c:3871
Code: c3 e8 b8 e9 72 fb 0f 0b e9 49 fe ff ff e8 ac e9 72 fb 0f 0b e9 cd fd  
ff ff e8 a0 e9 72 fb 0f 0b e9 00 ff ff ff e8 94 e9 72 fb <0f> 0b e9 62 fd  
ff ff e8 98 e8 a9 fb e9 7d fe ff ff 4c 89 ff e8 ab
kobject: 'loop1' (00000000fd200829): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
RSP: 0018:ffff8880a9a8fbb0 EFLAGS: 00010293
RAX: ffff8880a9a82100 RBX: ffff88808e30dbf0 RCX: 1ffff1101535053e
RDX: 0000000000000000 RSI: ffffffff85fcf7ec RDI: ffff8880a9a8297c
RBP: ffff8880a9a8fbf0 R08: ffff8880a9a82100 R09: ffff8880a9a829f0
R10: 0000000000000000 R11: 0000000000000000 R12: ffff88808e30c080
R13: ffff8880a9a8fcc8 R14: ffffffff893d5eb8 R15: dffffc0000000000
 xfrm_net_exit+0x1d/0x70 net/xfrm/xfrm_policy.c:3931
 ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:153
 cleanup_net+0x3fb/0x960 net/core/net_namespace.c:551
kobject: 'loop1' (00000000fd200829): kobject_uevent_env
kobject: 'loop1' (00000000fd200829): fill_kobj_path: path  
= '/devices/virtual/block/loop1'
cgroup: fork rejected by pids controller in /syz1
 process_one_work+0x98e/0x1790 kernel/workqueue.c:2173
 worker_thread+0x98/0xe40 kernel/workqueue.c:2319
 kthread+0x357/0x430 kernel/kthread.c:246
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352
Kernel Offset: disabled
Rebooting in 86400 seconds..