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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff88803f99a4c4 by task syz.4.17545/7898

CPU: 0 UID: 0 PID: 7898 Comm: syz.4.17545 Not tainted 6.16.0-syzkaller-11895-gcca7a0aae895-dirty #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: 0033:0x7fafcdd8ebe9
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:00007fafcec35038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fafcdfb5fa0 RCX: 00007fafcdd8ebe9
RDX: 0000000000000000 RSI: 0000200000000180 RDI: 0000000000000005
RBP: 00007fafcde11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fafcdfb6038 R14: 00007fafcdfb5fa0 R15: 00007ffd49401b88
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3f99a
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x2dc2(GFP_KERNEL|__GFP_HIGHMEM|__GFP_ZERO|__GFP_NOWARN), pid 7720, tgid 7719 (syz.4.17467), ts 1575581220239, free_ts 1575643276129
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 alloc_pages_noprof+0xa9/0x190
 __vmalloc_node_range_noprof+0x97d/0x12f0
 __vmalloc_noprof+0xb1/0xf0
 pcpu_create_chunk+0x34c/0xbf0
 pcpu_alloc_noprof+0x789/0x16b0
 bpf_map_alloc_percpu+0xbc/0x1b0
 prealloc_init+0x225/0x630
 htab_map_alloc+0x6ce/0xc70
 map_create+0xaa3/0x14d0
 __sys_bpf+0x60f/0x870
 __x64_sys_bpf+0x7c/0x90
 do_syscall_64+0xfa/0x3b0
page last free pid 6548 tgid 6548 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 vfree+0x25a/0x400
 pcpu_balance_free+0x6ae/0x940
 pcpu_balance_workfn+0xd01/0xe00
 process_scheduled_works+0xae1/0x17b0
 worker_thread+0x8a0/0xda0
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30

Memory state around the buggy address:
 ffff88803f99a380: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803f99a400: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88803f99a480: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff88803f99a500: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803f99a580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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