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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff8881272d6944 by task syz.2.8914/26583

CPU: 1 UID: 0 PID: 26583 Comm: syz.2.8914 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: 0033:0x7fc82298ebe9
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:00007fc8238cf038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fc822bc5fa0 RCX: 00007fc82298ebe9
RDX: 0000000000000010 RSI: 0000200000000640 RDI: 0000000000000003
RBP: 00007fc822a11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc822bc6038 R14: 00007fc822bc5fa0 R15: 00007ffd7db8dc08
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x200000021 pfn:0x1272d6
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 ffffea0004a71608 ffffea00041f8f08 0000000000000000
raw: 0000000200000021 ffff8881100a47e0 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 0x440dc0(GFP_KERNEL_ACCOUNT|__GFP_ZERO|__GFP_COMP), pid 26547, tgid 26547 (syz-executor), ts 431227115690, free_ts 431299946141
 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
 pte_alloc_one+0x21/0x170
 __handle_mm_fault+0x2795/0x5440
 handle_mm_fault+0x40a/0x8e0
 do_user_addr_fault+0xa81/0x1390
 exc_page_fault+0x76/0xf0
 asm_exc_page_fault+0x26/0x30
page last free pid 26540 tgid 26539 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __tlb_remove_table+0x2d2/0x3b0
 tlb_remove_table_rcu+0x85/0x100
 rcu_core+0xcab/0x1770
 handle_softirqs+0x286/0x870
 __irq_exit_rcu+0xca/0x1f0
 irq_exit_rcu+0x9/0x30
 sysvec_apic_timer_interrupt+0xa6/0xc0
 asm_sysvec_apic_timer_interrupt+0x1a/0x20

Memory state around the buggy address:
 ffff8881272d6800: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881272d6880: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff8881272d6900: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff8881272d6980: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff8881272d6a00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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