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BUG: KFENCE: use-after-free read in xfrm_alloc_spi+0x3b9/0xf30

Use-after-free read at 0xffff88813655e0c4 (in kfence-#174):
 xfrm_alloc_spi+0x3b9/0xf30
 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

kfence-#174: 0xffff88813655efe0-0xffff88813655eff7, size=24, cache=kmalloc-32

allocated by task 5857 on cpu 0 at 120.657906s (5.886208s ago):
 kmem_cache_free+0x166/0x400
 fput_close_sync+0x119/0x200
 __x64_sys_close+0x7f/0x110
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

freed by task 9188 on cpu 0 at 120.683590s (5.872556s ago):
 slab_free_after_rcu_debug+0x60/0x2a0
 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
 _raw_spin_unlock_irqrestore+0xa8/0x110
 pcpu_alloc_noprof+0xc00/0x16b0
 fib6_nh_init+0x78c/0x1ff0
 ip6_route_info_create_nh+0x16a/0xab0
 addrconf_f6i_alloc+0x203/0x450
 ipv6_add_addr+0x56e/0x1090
 addrconf_add_linklocal+0x28c/0x6c0
 addrconf_addr_gen+0x46f/0x580
 addrconf_init_auto_addrs+0x62d/0xa30
 addrconf_notify+0xacc/0x1010
 notifier_call_chain+0x1b6/0x3e0
 __dev_notify_flags+0x18d/0x2e0
 netif_change_flags+0xe8/0x1a0
 dev_change_flags+0x130/0x260
 devinet_ioctl+0xbb4/0x1b50
 inet_ioctl+0x3c0/0x4c0
 sock_do_ioctl+0xdc/0x300
 sock_ioctl+0x576/0x790
 __se_sys_ioctl+0xfc/0x170
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 0 UID: 0 PID: 9587 Comm: syz.1.1568 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
RIP: 0010:xfrm_alloc_spi+0x3b9/0xf30
Code: c1 08 c1 74 0a e8 97 2c 9e f7 e9 14 02 00 00 49 8d 9d c4 00 00 00 48 89 d8 48 c1 e8 03 42 0f b6 04 20 84 c0 0f 85 9f 01 00 00 <8b> 1b 89 df 44 89 f6 e8 2b 2e 9e f7 44 39 f3 0f 85 df 00 00 00 49
RSP: 0018:ffffc90007c570e0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffff88813655e0c4 RCX: 0000000000080000
RDX: ffffc90020001000 RSI: 0000000000000207 RDI: 0000000000000208
RBP: ffffc90007c57230 R08: 0000000000000000 R09: ffffffff8a217ea0
R10: dffffc0000000000 R11: fffff52000f8ae0c R12: dffffc0000000000
R13: ffff88813655e000 R14: 0000000000000000 R15: ffffc90007c576a0
FS:  00007f440da006c0(0000) GS:ffff8880b861c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff88813655e0c4 CR3: 0000000108564000 CR4: 00000000000006f0
Call Trace:
 <TASK>
 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: 0033:0x7f440cb8ebe9
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:00007f440da00038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f440cdb6090 RCX: 00007f440cb8ebe9
RDX: 0000000000000000 RSI: 0000200000000440 RDI: 0000000000000005
RBP: 00007f440cc11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f440cdb6128 R14: 00007f440cdb6090 R15: 00007ffe3c0d9fb8
 </TASK>
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