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BUG: KASAN: use-after-free in perf_output_read_group kernel/events/core.c:5882 [inline]
BUG: KASAN: use-after-free in perf_output_read+0xe58/0xfc0 kernel/events/core.c:5917
Read of size 8 at addr ffff8881c659b008 by task syz-executor.2/28248

CPU: 0 PID: 28248 Comm: syz-executor.2 Not tainted 4.14.125+ #6
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0xb9/0x10e lib/dump_stack.c:53
 print_address_description+0x60/0x226 mm/kasan/report.c:252
 kasan_report_error mm/kasan/report.c:351 [inline]
 kasan_report mm/kasan/report.c:409 [inline]
 kasan_report.cold+0xae/0x2d5 mm/kasan/report.c:393

Allocated by task 19916:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_kmalloc.part.0+0x4f/0xd0 mm/kasan/kasan.c:551
 kmem_cache_alloc_trace+0x126/0x310 mm/slub.c:2750
 kmalloc include/linux/slab.h:488 [inline]
 kzalloc include/linux/slab.h:661 [inline]
 ep_alloc fs/eventpoll.c:1035 [inline]
 SYSC_epoll_create1 fs/eventpoll.c:1972 [inline]
 SyS_epoll_create1+0xbb/0x370 fs/eventpoll.c:1958
 do_syscall_64+0x19b/0x510 arch/x86/entry/common.c:292

Freed by task 19916:
 save_stack mm/kasan/kasan.c:447 [inline]
 set_track mm/kasan/kasan.c:459 [inline]
 kasan_slab_free+0xb0/0x190 mm/kasan/kasan.c:524
 slab_free_hook mm/slub.c:1389 [inline]
 slab_free_freelist_hook mm/slub.c:1410 [inline]
 slab_free mm/slub.c:2966 [inline]
 kfree+0xf5/0x310 mm/slub.c:3897
 ep_eventpoll_release+0x41/0x60 fs/eventpoll.c:879
 __fput+0x25e/0x700 fs/file_table.c:210
 task_work_run+0x118/0x190 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:191 [inline]
 exit_to_usermode_loop+0x13b/0x160 arch/x86/entry/common.c:164
 prepare_exit_to_usermode arch/x86/entry/common.c:199 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:270 [inline]
 do_syscall_64+0x392/0x510 arch/x86/entry/common.c:297

The buggy address belongs to the object at ffff8881c659af00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 264 bytes inside of
 512-byte region [ffff8881c659af00, ffff8881c659b100)
The buggy address belongs to the page:
page:ffffea0007196680 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000000000000 00000001000c000c
raw: ffffea000721a480 0000000c0000000c ffff8881da802c00 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c659af00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881c659af80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff8881c659b000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff8881c659b080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881c659b100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
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