audit: type=1400 audit(1596907440.673:8): avc:  denied  { execmem } for  pid=6481 comm="syz-executor804" scontext=system_u:system_r:kernel_t:s0 tcontext=system_u:system_r:kernel_t:s0 tclass=process permissive=1
==================================================================
BUG: KASAN: stack-out-of-bounds in get_reg arch/x86/kernel/unwind_orc.c:391 [inline]
BUG: KASAN: stack-out-of-bounds in unwind_next_frame+0x161c/0x1c60 arch/x86/kernel/unwind_orc.c:557
Read of size 8 at addr ffff8880848df7f8 by task syz-executor804/6483

CPU: 0 PID: 6483 Comm: syz-executor804 Not tainted 4.19.138-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1fc/0x2fe lib/dump_stack.c:118
 print_address_description.cold+0x54/0x219 mm/kasan/report.c:256
 kasan_report_error.cold+0x8a/0x1c7 mm/kasan/report.c:354
 kasan_report mm/kasan/report.c:412 [inline]
 __asan_report_load8_noabort+0x88/0x90 mm/kasan/report.c:433
 get_reg arch/x86/kernel/unwind_orc.c:391 [inline]
 unwind_next_frame+0x161c/0x1c60 arch/x86/kernel/unwind_orc.c:557
 perf_callchain_kernel+0x3fa/0x5c0 arch/x86/events/core.c:2346
 get_perf_callchain+0x392/0x860 kernel/events/callchain.c:202
 perf_callchain+0x165/0x1c0 kernel/events/core.c:6448
 perf_prepare_sample+0x81e/0x1620 kernel/events/core.c:6475
 __perf_event_output kernel/events/core.c:6590 [inline]
 perf_event_output_forward+0xf3/0x270 kernel/events/core.c:6608
 __perf_event_overflow+0x13c/0x370 kernel/events/core.c:7881
 perf_swevent_overflow kernel/events/core.c:7957 [inline]
 perf_swevent_event+0x4b9/0x550 kernel/events/core.c:7995
 perf_tp_event+0x29f/0xaa0 kernel/events/core.c:8413
 perf_trace_run_bpf_submit+0x144/0x220 kernel/events/core.c:8387
 perf_trace_lock_acquire+0x36b/0x530 include/trace/events/lock.h:13
 trace_lock_acquire include/trace/events/lock.h:13 [inline]
 lock_acquire+0x298/0x3c0 kernel/locking/lockdep.c:3906
 __raw_spin_lock_irqsave include/linux/spinlock_api_smp.h:110 [inline]
 _raw_spin_lock_irqsave+0x8c/0xc0 kernel/locking/spinlock.c:152
 __debug_check_no_obj_freed lib/debugobjects.c:776 [inline]
 debug_check_no_obj_freed+0xb5/0x482 lib/debugobjects.c:817
 free_pages_prepare mm/page_alloc.c:1055 [inline]
 free_pcp_prepare mm/page_alloc.c:1069 [inline]
 free_unref_page_prepare+0x1ea/0x5d0 mm/page_alloc.c:2757
 free_unref_page+0x20/0x170 mm/page_alloc.c:2806
 pte_free arch/x86/include/asm/pgalloc.h:65 [inline]
 zap_deposited_table mm/huge_memory.c:1739 [inline]
 zap_huge_pmd+0xa00/0xe90 mm/huge_memory.c:1793
 zap_pmd_range mm/memory.c:1427 [inline]
 zap_pud_range mm/memory.c:1469 [inline]
 zap_p4d_range mm/memory.c:1490 [inline]
 unmap_page_range+0xe4d/0x2a70 mm/memory.c:1511
 unmap_single_vma+0x198/0x300 mm/memory.c:1556
 unmap_vmas+0xa9/0x180 mm/memory.c:1586
 exit_mmap+0x2b9/0x510 mm/mmap.c:3091
 __mmput kernel/fork.c:1015 [inline]
 mmput+0x14e/0x4a0 kernel/fork.c:1036
 exit_mm kernel/exit.c:546 [inline]
 do_exit+0xab5/0x2b70 kernel/exit.c:874
 do_group_exit+0x125/0x310 kernel/exit.c:990
 __do_sys_exit_group kernel/exit.c:1001 [inline]
 __se_sys_exit_group kernel/exit.c:999 [inline]
 __x64_sys_exit_group+0x3a/0x50 kernel/exit.c:999
 do_syscall_64+0xf9/0x620 arch/x86/entry/common.c:293
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x43ffc8
Code: Bad RIP value.
RSP: 002b:00007ffc3e9f7658 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 000000000043ffc8
RDX: 0000000000000000 RSI: 000000000000003c RDI: 0000000000000000
RBP: 00000000004bf850 R08: 00000000000000e7 R09: ffffffffffffffd0
R10: 00000000004002c8 R11: 0000000000000246 R12: 0000000000000001
R13: 00000000006d1180 R14: 0000000000000000 R15: 0000000000000000

The buggy address belongs to the page:
page:ffffea00021237c0 count:0 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000000()
raw: 00fffe0000000000 0000000000000000 ffffffff02120101 0000000000000000
raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8880848df680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880848df700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff8880848df780: 00 00 00 00 00 f1 f1 f1 f1 f1 f1 04 f2 00 f3 f3
                                                                ^
 ffff8880848df800: f3 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff8880848df880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
==================================================================