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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff8881099c8544 by task syz.1.3746/24219

CPU: 0 UID: 0 PID: 24219 Comm: syz.1.3746 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
Call Trace:
 <TASK>
 dump_stack_lvl+0x189/0x250
 print_report+0xca/0x240
 kasan_report+0x118/0x150
 xfrm_alloc_spi+0x570/0xf30
 xfrm_alloc_userspi+0x70b/0xc90
 xfrm_user_rcv_msg+0x7a3/0xab0
 netlink_rcv_skb+0x208/0x470
 xfrm_netlink_rcv+0x79/0x90
 netlink_unicast+0x82f/0x9e0
 netlink_sendmsg+0x805/0xb30
 __sock_sendmsg+0x21c/0x270
 ____sys_sendmsg+0x505/0x830
 ___sys_sendmsg+0x21f/0x2a0
 __x64_sys_sendmsg+0x19b/0x260
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2b3a58eba9
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:00007f2b387f6038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f2b3a7d5fa0 RCX: 00007f2b3a58eba9
RDX: 0000000000000000 RSI: 00002000000004c0 RDI: 0000000000000008
RBP: 00007f2b3a611e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f2b3a7d6038 R14: 00007f2b3a7d5fa0 R15: 00007ffcfd4e20d8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff8881099c9680 pfn:0x1099c8
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
page_type: f0(buddy)
raw: 057ff00000000000 ffffea00048a4108 ffffea0004369b08 0000000000000000
raw: ffff8881099c9680 0000000000000002 00000000f0000000 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x52820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 7713, tgid 7712 (syz.1.381), ts 104241049131, free_ts 680900161619
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x370
 ___slab_alloc+0xbeb/0x1420
 kmem_cache_alloc_noprof+0x283/0x3c0
 xfrm_state_alloc+0x24/0x2f0
 xfrm_add_acquire+0xf7/0xb20
 xfrm_user_rcv_msg+0x7a3/0xab0
 netlink_rcv_skb+0x208/0x470
 xfrm_netlink_rcv+0x79/0x90
 netlink_unicast+0x82f/0x9e0
 netlink_sendmsg+0x805/0xb30
 __sock_sendmsg+0x21c/0x270
 ____sys_sendmsg+0x505/0x830
page last free pid 22857 tgid 22856 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __slab_free+0x303/0x3c0
 qlist_free_all+0x97/0x140
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 __kmalloc_cache_noprof+0x1be/0x3d0
 ref_tracker_alloc+0x133/0x460
 netdev_queue_update_kobjects+0x1d1/0x6c0
 netdev_register_kobject+0x258/0x310
 register_netdevice+0x126c/0x1ae0
 __ip_tunnel_create+0x3e7/0x560
 ip_tunnel_init_net+0x2ba/0x800
 vti_init_net+0x2f/0x100
 ops_init+0x35c/0x5c0
 setup_net+0x10c/0x320
 copy_net_ns+0x31b/0x4d0

Memory state around the buggy address:
 ffff8881099c8400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881099c8480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881099c8500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8881099c8580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881099c8600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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