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BUG: KASAN: use-after-free in xfrm_alloc_spi+0x570/0xf30
Read of size 4 at addr ffff88803bfe2dc4 by task syz.2.1586/11960

CPU: 1 UID: 0 PID: 11960 Comm: syz.2.1586 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: 0033:0x7f7f1ff8ebe9
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:00007f7f20ee0038 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f7f201b5fa0 RCX: 00007f7f1ff8ebe9
RDX: 0000000020000000 RSI: 0000200000000040 RDI: 0000000000000005
RBP: 00007f7f20011e19 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f7f201b6038 R14: 00007f7f201b5fa0 R15: 00007ffe552babf8
 </TASK>

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x3bfe2
flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
raw: 00fff00000000000 0000000000000000 ffffea0000eff890 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as freed
page last allocated via order 2, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 11003, tgid 11001 (syz.2.1334), ts 130947149802, free_ts 133654708207
 post_alloc_hook+0x240/0x2a0
 get_page_from_freelist+0x21e4/0x22c0
 __alloc_frozen_pages_noprof+0x181/0x370
 alloc_pages_mpol+0x232/0x4a0
 allocate_slab+0x8a/0x370
 ___slab_alloc+0xbeb/0x1410
 __kmalloc_noprof+0x305/0x4f0
 copy_splice_read+0x143/0xa50
 splice_direct_to_actor+0x4d0/0xcc0
 do_splice_direct+0x181/0x270
 do_sendfile+0x4da/0x7e0
 __se_sys_sendfile64+0x13e/0x190
 do_syscall_64+0xfa/0x3b0
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
page last free pid 11144 tgid 11143 stack trace:
 __free_frozen_pages+0xbc4/0xd30
 __put_partials+0x156/0x1a0
 put_cpu_partial+0x17c/0x250
 __slab_free+0x2d5/0x3c0
 qlist_free_all+0x97/0x140
 kasan_quarantine_reduce+0x148/0x160
 __kasan_slab_alloc+0x22/0x80
 kmem_cache_alloc_node_noprof+0x1bb/0x3c0
 __alloc_skb+0x112/0x2d0
 alloc_skb_with_frags+0xca/0x890
 sock_alloc_send_pskb+0x857/0x990
 j1939_sk_sendmsg+0x6f5/0x1350
 __sock_sendmsg+0x21c/0x270
 ____sys_sendmsg+0x52d/0x830
 ___sys_sendmsg+0x21f/0x2a0
 __sys_sendmmsg+0x227/0x430

Memory state around the buggy address:
 ffff88803bfe2c80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803bfe2d00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
>ffff88803bfe2d80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
                                           ^
 ffff88803bfe2e00: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
 ffff88803bfe2e80: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff
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