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BUG: KFENCE: use-after-free read in __xfrm_state_insert+0x855/0x1450

Use-after-free read at 0xffff888136558330 (in kfence-#171):
 __xfrm_state_insert+0x855/0x1450
 xfrm_state_insert+0x54/0x60
 ipcomp6_init_state+0x655/0x900
 __xfrm_init_state+0xa76/0x13f0
 xfrm_add_sa+0x2f5b/0x4070
 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-#171: 0xffff888136558000-0xffff8881365580ef, size=240, cache=skbuff_head_cache

allocated by task 5827 on cpu 0 at 278.820641s (2.140977s ago):
 __alloc_skb+0x112/0x2d0
 __tcp_send_ack+0xaf/0x620
 tcp_recvmsg_locked+0x2d7f/0x3660
 tcp_recvmsg+0x216/0x810
 inet_recvmsg+0x147/0x250
 sock_recvmsg+0x1a8/0x270
 sock_read_iter+0x231/0x2f0
 vfs_read+0x55a/0xa30
 ksys_read+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

freed by task 5827 on cpu 0 at 278.820869s (2.163547s ago):
 tcp_rcv_established+0xe9e/0x1eb0
 tcp_v4_do_rcv+0xa23/0xce0
 tcp_v4_rcv+0x26a6/0x2f40
 ip_protocol_deliver_rcu+0x221/0x440
 ip_local_deliver_finish+0x3bb/0x6f0
 NF_HOOK+0x30c/0x3a0
 NF_HOOK+0x30c/0x3a0
 __netif_receive_skb+0x143/0x380
 process_backlog+0x60e/0x14f0
 __napi_poll+0xc7/0x360
 net_rx_action+0x707/0xe30
 handle_softirqs+0x286/0x870
 do_softirq+0xec/0x180
 __local_bh_enable_ip+0x17d/0x1c0
 __dev_queue_xmit+0x1d79/0x3b50
 ip_finish_output2+0xd03/0x1160
 ip_output+0x2a1/0x3c0
 __ip_queue_xmit+0x1106/0x1b00
 __tcp_transmit_skb+0x2215/0x3680
 tcp_recvmsg_locked+0x2d7f/0x3660
 tcp_recvmsg+0x216/0x810
 inet_recvmsg+0x147/0x250
 sock_recvmsg+0x1a8/0x270
 sock_read_iter+0x231/0x2f0
 vfs_read+0x55a/0xa30
 ksys_read+0x145/0x250
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

CPU: 1 UID: 0 PID: 13863 Comm: syz.4.3438 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_state_insert+0x855/0x1450
Code: d8 0f 94 c1 08 c1 74 0a e8 98 e1 9e f7 e9 aa 00 00 00 4d 8d ac 24 30 03 00 00 4d 89 ee 49 c1 ee 03 41 0f b6 04 1e 84 c0 75 48 <41> 0f b6 6d 00 83 e5 0c bf 08 00 00 00 89 ee e8 67 e4 9e f7 83 fd
RSP: 0018:ffffc9000358f0f8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: dffffc0000000000 RCX: 0000000000000000
RDX: ffff8880229d1cc0 RSI: 0000000000000000 RDI: 0000000000000008
RBP: 0000000000000004 R08: dffffc0000000000 R09: 0000000000000002
R10: 000000000000000a R11: 0000000000000002 R12: ffff888136558000
R13: ffff888136558330 R14: 1ffff11026cab066 R15: 0000000000000004
FS:  00007fc23bab96c0(0000) GS:ffff8881a3c1c000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff888136558330 CR3: 000000011204e000 CR4: 00000000000006f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000600
Call Trace:
 <TASK>
 xfrm_state_insert+0x54/0x60
 ipcomp6_init_state+0x655/0x900
 __xfrm_init_state+0xa76/0x13f0
 xfrm_add_sa+0x2f5b/0x4070
 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: 0033:0x7fc23ab8ebe9
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:00007fc23bab9038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fc23adb5fa0 RCX: 00007fc23ab8ebe9
RDX: 0000000000000000 RSI: 0000200000000040 RDI: 0000000000000006
RBP: 00007fc23ac11e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc23adb6038 R14: 00007fc23adb5fa0 R15: 00007fff81157498
 </TASK>
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