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BUG: KASAN: use-after-free in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:259 [inline]
BUG: KASAN: use-after-free in put_task_struct include/linux/sched/task.h:95 [inline]
BUG: KASAN: use-after-free in _free_event+0x49a/0x15e0 kernel/events/core.c:4451
Write of size 4 at addr ffff8801d559e5a0 by task syz-executor7/14002

CPU: 1 PID: 14002 Comm: syz-executor7 Not tainted 4.18.0-next-20180820+ #43
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+0x1c9/0x2b4 lib/dump_stack.c:113
QAT: Invalid ioctl
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
QAT: Invalid ioctl
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x30d mm/kasan/report.c:412
 check_memory_region_inline mm/kasan/kasan.c:260 [inline]
 check_memory_region+0x13e/0x1b0 mm/kasan/kasan.c:267
 kasan_check_write+0x14/0x20 mm/kasan/kasan.c:278
 atomic_dec_and_test include/asm-generic/atomic-instrumented.h:259 [inline]
 put_task_struct include/linux/sched/task.h:95 [inline]
 _free_event+0x49a/0x15e0 kernel/events/core.c:4451
QAT: Invalid ioctl
 free_event+0xb4/0x180 kernel/events/core.c:4472
 perf_event_release_kernel+0x7d5/0xfc0 kernel/events/core.c:4633
QAT: Invalid ioctl
 perf_release+0x37/0x50 kernel/events/core.c:4647
 __fput+0x376/0x8a0 fs/file_table.c:279
 ____fput+0x15/0x20 fs/file_table.c:312
 task_work_run+0x1e8/0x2a0 kernel/task_work.c:113
 exit_task_work include/linux/task_work.h:22 [inline]
 do_exit+0x1ae4/0x26e0 kernel/exit.c:871
 do_group_exit+0x177/0x440 kernel/exit.c:974
 get_signal+0x851/0x18e0 kernel/signal.c:2513
 do_signal+0x9c/0x21c0 arch/x86/kernel/signal.c:816
 exit_to_usermode_loop+0x2e5/0x380 arch/x86/entry/common.c:162
 prepare_exit_to_usermode+0x342/0x3b0 arch/x86/entry/common.c:197
 retint_user+0x8/0x18
RIP: 0033:0x457095
Code: 8b 4c 24 18 48 8b 54 24 38 48 8b 7c 24 48 eb 8d 48 8b 6c 24 50 48 83 c4 58 c3 48 89 04 24 48 89 5c 24 08 e8 0d a9 fb ff 48 8b <44> 24 40 48 8b 4c 24 48 48 8b 54 24 38 4c 8b 54 24 18 e9 ee fe ff
RSP: 002b:00000000200001c0 EFLAGS: 00010217
RAX: 0000000000000000 RBX: 00007fc22840c6d4 RCX: 0000000000457089
RDX: 00000000200000c0 RSI: 00000000200001c0 RDI: 0400000000040000
RBP: 00000000009300a0 R08: 0000000020000040 R09: 0000000000000000
R10: 0000000020000080 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004cb448 R14: 00000000004c3092 R15: 0000000000000000

Allocated by task 14001:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 kasan_kmalloc+0xc4/0xe0 mm/kasan/kasan.c:553
 kasan_slab_alloc+0x12/0x20 mm/kasan/kasan.c:490
 kmem_cache_alloc_node+0x144/0x720 mm/slab.c:3644
 alloc_task_struct_node kernel/fork.c:158 [inline]
 dup_task_struct kernel/fork.c:804 [inline]
 copy_process+0x1dd0/0x7ae0 kernel/fork.c:1711
 _do_fork+0x1ca/0x1170 kernel/fork.c:2172
 __do_sys_clone kernel/fork.c:2279 [inline]
 __se_sys_clone kernel/fork.c:2273 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2273
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

Freed by task 14001:
 save_stack+0x43/0xd0 mm/kasan/kasan.c:448
 set_track mm/kasan/kasan.c:460 [inline]
 __kasan_slab_free+0x11a/0x170 mm/kasan/kasan.c:521
 kasan_slab_free+0xe/0x10 mm/kasan/kasan.c:528
 __cache_free mm/slab.c:3498 [inline]
 kmem_cache_free+0x86/0x280 mm/slab.c:3756
 free_task_struct kernel/fork.c:163 [inline]
 free_task+0x16e/0x1f0 kernel/fork.c:417
 copy_process+0x1b21/0x7ae0 kernel/fork.c:2104
 _do_fork+0x1ca/0x1170 kernel/fork.c:2172
 __do_sys_clone kernel/fork.c:2279 [inline]
 __se_sys_clone kernel/fork.c:2273 [inline]
 __x64_sys_clone+0xbf/0x150 kernel/fork.c:2273
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe

The buggy address belongs to the object at ffff8801d559e580
 which belongs to the cache task_struct of size 6016
The buggy address is located 32 bytes inside of
 6016-byte region [ffff8801d559e580, ffff8801d559fd00)
The buggy address belongs to the page:
page:ffffea0007556780 count:1 mapcount:0 mapping:ffff8801dad49200 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea0006301388 ffffea0006e1a788 ffff8801dad49200
raw: 0000000000000000 ffff8801d559e580 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8801d559e480: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801d559e500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801d559e580: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8801d559e600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801d559e680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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