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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff888028aff6c4 by task syz.2.3813/15937

CPU: 1 UID: 0 PID: 15937 Comm: syz.2.3813 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
 pfkey_getspi+0x7a8/0xee0
 pfkey_sendmsg+0xbfe/0x1090
 __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: 0033:0x7fc0e818eba9
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:00007fc0e8f5e038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fc0e83d5fa0 RCX: 00007fc0e818eba9
RDX: 00000000200c405a RSI: 00002000000001c0 RDI: 0000000000000004
RBP: 00007fc0e8211e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc0e83d6038 R14: 00007fc0e83d5fa0 R15: 00007ffe9dc9fc18
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x50c pfn:0x28aff
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 dead000000000100 dead000000000122 0000000000000000
raw: 000000000000050c 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 0x540dc0(GFP_USER|__GFP_ZERO|__GFP_COMP|__GFP_ACCOUNT), pid 14611, tgid 14611 (syz-executor), ts 375432505205, free_ts 375561852273
 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
 __pte_alloc+0x25/0x1a0
 copy_pmd_range+0x6a91/0x71d0
 copy_page_range+0xc14/0x1270
 dup_mmap+0xf57/0x1ac0
 copy_mm+0x13c/0x4b0
 copy_process+0x1706/0x3c00
 kernel_clone+0x21e/0x840
 __x64_sys_clone+0x18b/0x1e0
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 23 tgid 23 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
 run_ksoftirqd+0x9b/0x100
 smpboot_thread_fn+0x542/0xa60
 kthread+0x711/0x8a0
 ret_from_fork+0x3fc/0x770
 ret_from_fork_asm+0x1a/0x30

Memory state around the buggy address:
 ffff888028aff580: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888028aff600: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888028aff680: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888028aff700: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888028aff780: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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