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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff888039b9bb44 by task syz.3.6977/29440

CPU: 1 UID: 0 PID: 29440 Comm: syz.3.6977 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: 0033:0x7fb1c478ebe9
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:00007fb1c56b2038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fb1c49b5fa0 RCX: 00007fb1c478ebe9
RDX: 0000000000000000 RSI: 00002000000001c0 RDI: 0000000000000003
RBP: 00007fb1c4811e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fb1c49b6038 R14: 00007fb1c49b5fa0 R15: 00007fff265eb1a8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0xffff888039b9bf00 pfn:0x39b9b
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 ffffea0000f1e008 ffffea00009d7308 0000000000000000
raw: ffff888039b9bf00 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 0x406dc2(GFP_KERNEL_ACCOUNT|__GFP_HIGHMEM|__GFP_ZERO|__GFP_NOWARN|__GFP_RETRY_MAYFAIL), pid 29437, tgid 29435 (syz.3.6976), ts 627988387943, free_ts 628012912826
 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
 bpf_map_area_alloc+0x12d/0x180
 prealloc_init+0x123/0x630
 htab_map_alloc+0x6ce/0xc70
 map_create+0xaa3/0x14d0
 __sys_bpf+0x60f/0x870
 __x64_sys_bpf+0x7c/0x90
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 13090 tgid 13090 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 vfree+0x25a/0x400
 htab_map_free+0x7b2/0x980
 bpf_map_free_deferred+0x113/0x140
 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:
 ffff888039b9ba00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888039b9ba80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff888039b9bb00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff888039b9bb80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff888039b9bc00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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