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BUG: KASAN: stack-out-of-bounds in deref_stack_regs arch/x86/kernel/unwind_orc.c:290 [inline]
BUG: KASAN: stack-out-of-bounds in unwind_next_frame+0x1595/0x1930 arch/x86/kernel/unwind_orc.c:420
Read of size 8 at addr ffff8881c4c276b8 by task syz-executor830/2462

CPU: 0 PID: 2462 Comm: syz-executor830 Not tainted 4.14.90+ #29
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x11b lib/dump_stack.c:53
 print_address_description+0x60/0x22b mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report.cold.6+0x11b/0x2dd mm/kasan/report.c:409
 deref_stack_regs arch/x86/kernel/unwind_orc.c:290 [inline]
 unwind_next_frame+0x1595/0x1930 arch/x86/kernel/unwind_orc.c:420
 perf_callchain_kernel+0x39c/0x540 arch/x86/events/core.c:2334
 get_perf_callchain+0x2eb/0x760 kernel/events/callchain.c:217
 perf_callchain+0x14a/0x190 kernel/events/callchain.c:190
 perf_prepare_sample+0x704/0x13c0 kernel/events/core.c:6140
 __perf_event_output kernel/events/core.c:6256 [inline]
 perf_event_output_forward+0xeb/0x230 kernel/events/core.c:6274
 __perf_event_overflow+0x116/0x320 kernel/events/core.c:7510
 perf_swevent_overflow+0x166/0x1f0 kernel/events/core.c:7586
 perf_swevent_event+0x112/0x270 kernel/events/core.c:7624
 perf_tp_event+0x620/0x7e0 kernel/events/core.c:8048
 perf_trace_run_bpf_submit+0x10f/0x170 kernel/events/core.c:8018
 perf_trace_lock+0x2f6/0x4c0 include/trace/events/lock.h:39
 trace_lock_release include/trace/events/lock.h:58 [inline]
 lock_release+0x4dc/0x720 kernel/locking/lockdep.c:4009
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:158 [inline]
 _raw_spin_unlock_irqrestore+0x1b/0x70 kernel/locking/spinlock.c:192
 __debug_check_no_obj_freed lib/debugobjects.c:760 [inline]
 debug_check_no_obj_freed+0x2b2/0x77c lib/debugobjects.c:776
 slab_free_hook mm/slub.c:1382 [inline]
 slab_free_freelist_hook mm/slub.c:1410 [inline]
 slab_free mm/slub.c:2966 [inline]
 kmem_cache_free+0x218/0x350 mm/slub.c:2988
 kfree_skbmem+0x9e/0x100 net/core/skbuff.c:582
 __kfree_skb net/core/skbuff.c:642 [inline]
 kfree_skb+0xd0/0x340 net/core/skbuff.c:659
 tun_queue_purge+0x108/0x300 drivers/net/tun.c:531
 __tun_detach+0x3bc/0xd10 drivers/net/tun.c:563
 tun_detach drivers/net/tun.c:586 [inline]
 tun_chr_close+0x40/0x50 drivers/net/tun.c:2661
 __fput+0x25e/0x6f0 fs/file_table.c:210
 task_work_run+0x116/0x190 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x8fb/0x28c0 kernel/exit.c:865
 do_group_exit+0x100/0x2e0 kernel/exit.c:968
 get_signal+0x4e5/0x1470 kernel/signal.c:2348
 do_signal+0x8f/0x1660 arch/x86/kernel/signal.c:809
 exit_to_usermode_loop+0x116/0x150 arch/x86/entry/common.c:159
 prepare_exit_to_usermode arch/x86/entry/common.c:198 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:267 [inline]
 do_syscall_64+0x35d/0x4b0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x447b29
RSP: 002b:00007fd0f1ce8cf8 EFLAGS: 00000246 ORIG_RAX: 00000000000000ca
RAX: fffffffffffffe00 RBX: 00000000006dec28 RCX: 0000000000447b29
RDX: 0000000000000000 RSI: 0000000000000080 RDI: 00000000006dec28
RBP: 00000000006dec20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000006dec2c
R13: 00007ffd130a38cf R14: 00007fd0f1ce99c0 R15: 00000000006dec20

The buggy address belongs to the page:
page:ffffea00071309c0 count:0 mapcount:0 mapping:          (null) index:0x0
flags: 0x4000000000000000()
raw: 4000000000000000 0000000000000000 0000000000000000 00000000ffffffff
raw: 0000000000000000 ffffea00071309e0 0000000000000000 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c4c27580: 00 00 00 00 00 00 00 f1 f1 f1 f1 04 f2 f2 f2 f2
 ffff8881c4c27600: f2 f2 f2 00 f2 f2 f2 00 00 00 00 00 00 00 00 00
>ffff8881c4c27680: 00 00 00 00 00 f1 f1 f1 f1 04 f2 f2 f2 00 00 00
                                        ^
 ffff8881c4c27700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8881c4c27780: 00 00 00 00 00 00 f1 f1 f1 f1 00 f2 f2 f2 00 00
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