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BUG: KASAN: use-after-free in xfrm6_tunnel_free_spi net/ipv6/xfrm6_tunnel.c:208 [inline]
BUG: KASAN: use-after-free in xfrm6_tunnel_destroy+0x4e0/0x560 net/ipv6/xfrm6_tunnel.c:303
Read of size 8 at addr ffff8881ce2000b8 by task kworker/0:13/23766

CPU: 0 PID: 23766 Comm: kworker/0:13 Not tainted 4.14.156-syzkaller #0
Workqueue: events xfrm_state_gc_task
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xe5/0x154 lib/dump_stack.c:58
 print_address_description+0x60/0x226 mm/kasan/report.c:187
 __kasan_report.cold+0x1a/0x41 mm/kasan/report.c:316
 xfrm6_tunnel_free_spi net/ipv6/xfrm6_tunnel.c:208 [inline]
 xfrm6_tunnel_destroy+0x4e0/0x560 net/ipv6/xfrm6_tunnel.c:303
 xfrm_state_gc_destroy net/xfrm/xfrm_state.c:449 [inline]
 xfrm_state_gc_task+0x3d6/0x550 net/xfrm/xfrm_state.c:470
 process_one_work+0x7f1/0x1580 kernel/workqueue.c:2134
 worker_thread+0xdd/0xdf0 kernel/workqueue.c:2271
 kthread+0x31f/0x430 kernel/kthread.c:232
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:404

Allocated by task 9595:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_kmalloc.part.0+0x53/0xc0 mm/kasan/common.c:501
 kmalloc include/linux/slab.h:493 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 ops_init+0xee/0x3f0 net/core/net_namespace.c:108
 setup_net+0x259/0x550 net/core/net_namespace.c:295
 copy_net_ns+0x195/0x480 net/core/net_namespace.c:419
 create_new_namespaces+0x373/0x760 kernel/nsproxy.c:107
 unshare_nsproxy_namespaces+0xa5/0x1e0 kernel/nsproxy.c:206
 SYSC_unshare kernel/fork.c:2543 [inline]
 SyS_unshare+0x34e/0x6c0 kernel/fork.c:2493
 do_syscall_64+0x19b/0x520 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
 0xffffffffffffffff

Freed by task 32762:
 save_stack mm/kasan/common.c:76 [inline]
 set_track mm/kasan/common.c:85 [inline]
 __kasan_slab_free+0x164/0x210 mm/kasan/common.c:463
 slab_free_hook mm/slub.c:1407 [inline]
 slab_free_freelist_hook mm/slub.c:1458 [inline]
 slab_free mm/slub.c:3039 [inline]
 kfree+0x108/0x3a0 mm/slub.c:3976
 ops_free net/core/net_namespace.c:132 [inline]
 ops_free_list.part.0+0x1f9/0x330 net/core/net_namespace.c:154
 ops_free_list net/core/net_namespace.c:152 [inline]
 cleanup_net+0x466/0x870 net/core/net_namespace.c:488
 process_one_work+0x7f1/0x1580 kernel/workqueue.c:2134
 worker_thread+0xdd/0xdf0 kernel/workqueue.c:2271
 kthread+0x31f/0x430 kernel/kthread.c:232
 ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:404
 0xffffffffffffffff

The buggy address belongs to the object at ffff8881ce200000
 which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 184 bytes inside of
 8192-byte region [ffff8881ce200000, ffff8881ce202000)
The buggy address belongs to the page:
page:ffffea0007388000 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000000000000 0000000100030003
raw: dead000000000100 dead000000000200 ffff8881da802400 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881ce1fff80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881ce200000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881ce200080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff8881ce200100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881ce200180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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