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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff8881126fd2c4 by task syz.1.4533/16174

CPU: 1 UID: 0 PID: 16174 Comm: syz.1.4533 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: 0033:0x7fad9898ebe9
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:00007fad997b7038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fad98bb5fa0 RCX: 00007fad9898ebe9
RDX: 0000000024000014 RSI: 0000200000000200 RDI: 0000000000000003
RBP: 00007fad98a11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fad98bb6038 R14: 00007fad98bb5fa0 R15: 00007ffd5c0e2b68
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffffffffffffffff pfn:0x1126fd
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 0000000000000000 00000000ffffffff 0000000000000000
raw: ffffffffffffffff 0000000000000000 00000000ffffffff 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 15887, tgid 15886 (syz.2.4402), ts 214786909360, free_ts 219031633292
 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/0x1410
 kmem_cache_alloc_node_noprof+0x280/0x3c0
 kmalloc_reserve+0xbd/0x290
 __alloc_skb+0x142/0x2d0
 fdb_notify+0xa6/0x160
 fdb_add_local+0x155/0x250
 br_fdb_add_local+0x3a/0x60
 __vlan_add+0x675/0x2660
 br_vlan_add+0x42c/0x950
 br_vlan_info+0x1b8/0x460
 br_process_vlan_info+0x600/0x890
page last free pid 16153 tgid 16153 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __put_partials+0x156/0x1a0
 put_cpu_partial+0x17c/0x250
 __slab_free+0x2d5/0x3c0
 qlist_free_all+0x97/0x140
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 kmem_cache_alloc_noprof+0x1c1/0x3c0
 __anon_vma_prepare+0xcb/0x4a0
 __handle_mm_fault+0x4b2d/0x5440
 handle_mm_fault+0x40a/0x8e0
 do_user_addr_fault+0xa81/0x1390
 exc_page_fault+0x76/0xf0
 asm_exc_page_fault+0x26/0x30

Memory state around the buggy address:
 ffff8881126fd180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881126fd200: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881126fd280: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8881126fd300: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881126fd380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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