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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+0x4f6/0x570 net/ipv6/xfrm6_tunnel.c:303
Read of size 8 at addr ffff8801ce68c9a0 by task kworker/1:2/4250

CPU: 1 PID: 4250 Comm: kworker/1:2 Not tainted 4.9.203-syzkaller #0
Workqueue: events xfrm_state_gc_task
 ffff88019fe8fa60 ffffffff81b55f6b 0000000000000000 ffffea000739a200
 ffff8801ce68c9a0 0000000000000008 ffffffff8277d966 ffff88019fe8fa98
 ffffffff8150c461 0000000000000000 ffff8801ce68c9a0 ffff8801ce68c9a0
Call Trace:
 [<0000000097a56a30>] __dump_stack lib/dump_stack.c:15 [inline]
 [<0000000097a56a30>] dump_stack+0xcb/0x130 lib/dump_stack.c:56
 [<0000000071d3d4b6>] print_address_description+0x6f/0x23a mm/kasan/report.c:256
 [<000000004ada9137>] kasan_report_error mm/kasan/report.c:355 [inline]
 [<000000004ada9137>] kasan_report mm/kasan/report.c:413 [inline]
 [<000000004ada9137>] kasan_report.cold+0x8c/0x2ba mm/kasan/report.c:397
 [<00000000fe55a533>] __asan_report_load8_noabort+0x14/0x20 mm/kasan/report.c:434
 [<000000003022f9d0>] xfrm6_tunnel_free_spi net/ipv6/xfrm6_tunnel.c:208 [inline]
 [<000000003022f9d0>] xfrm6_tunnel_destroy+0x4f6/0x570 net/ipv6/xfrm6_tunnel.c:303
 [<0000000042cbd443>] xfrm_state_gc_destroy net/xfrm/xfrm_state.c:368 [inline]
 [<0000000042cbd443>] xfrm_state_gc_task+0x3b9/0x520 net/xfrm/xfrm_state.c:388
 [<00000000bc3daa96>] process_one_work+0x88b/0x1600 kernel/workqueue.c:2114
 [<0000000059659526>] worker_thread+0x5df/0x11d0 kernel/workqueue.c:2251
 [<000000008fd6042d>] kthread+0x278/0x310 kernel/kthread.c:211
 [<00000000718e651d>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375

Allocated by task 8363:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack mm/kasan/kasan.c:512 [inline]
 set_track mm/kasan/kasan.c:524 [inline]
 kasan_kmalloc.part.0+0x62/0xf0 mm/kasan/kasan.c:616
 kasan_kmalloc+0xb7/0xd0 mm/kasan/kasan.c:601
 __kmalloc+0x133/0x320 mm/slub.c:3741
 kmalloc include/linux/slab.h:495 [inline]
 kzalloc include/linux/slab.h:636 [inline]
 ops_init+0xf1/0x3a0 net/core/net_namespace.c:101
 setup_net+0x1c8/0x500 net/core/net_namespace.c:292
 copy_net_ns+0x191/0x340 net/core/net_namespace.c:409
 create_new_namespaces+0x37c/0x7a0 kernel/nsproxy.c:106
 unshare_nsproxy_namespaces+0xab/0x1e0 kernel/nsproxy.c:205
 SYSC_unshare kernel/fork.c:2402 [inline]
 SyS_unshare+0x305/0x6f0 kernel/fork.c:2352
 do_syscall_64+0x1ad/0x5c0 arch/x86/entry/common.c:288
 entry_SYSCALL_64_after_swapgs+0x5d/0xdb

Freed by task 5133:
 save_stack_trace+0x16/0x20 arch/x86/kernel/stacktrace.c:57
 save_stack mm/kasan/kasan.c:512 [inline]
 set_track mm/kasan/kasan.c:524 [inline]
 kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:589
 slab_free_hook mm/slub.c:1355 [inline]
 slab_free_freelist_hook mm/slub.c:1377 [inline]
 slab_free mm/slub.c:2958 [inline]
 kfree+0xfc/0x310 mm/slub.c:3878
 ops_free net/core/net_namespace.c:126 [inline]
 ops_free_list.part.0+0x1ff/0x330 net/core/net_namespace.c:148
 ops_free_list net/core/net_namespace.c:146 [inline]
 cleanup_net+0x474/0x8a0 net/core/net_namespace.c:478
 process_one_work+0x88b/0x1600 kernel/workqueue.c:2114
 worker_thread+0x5df/0x11d0 kernel/workqueue.c:2251
 kthread+0x278/0x310 kernel/kthread.c:211
 ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:375

The buggy address belongs to the object at ffff8801ce68c200
 which belongs to the cache kmalloc-8192 of size 8192
The buggy address is located 1952 bytes inside of
 8192-byte region [ffff8801ce68c200, ffff8801ce68e200)
The buggy address belongs to the page:
page:ffffea000739a200 count:1 mapcount:0 mapping:          (null) index:0xffff8801ce688000 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801ce68c880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ce68c900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8801ce68c980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8801ce68ca00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801ce68ca80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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