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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+0xe4e/0xfc0 kernel/events/core.c:5917
Read of size 8 at addr ffff888192254f60 by task syz-executor.4/16251

CPU: 1 PID: 16251 Comm: syz-executor.4 Not tainted 4.14.123+ #2
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 14323:
 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]
 alloc_pipe_info+0xaa/0x380 fs/pipe.c:647
 splice_direct_to_actor+0x5b5/0x760 fs/splice.c:920
 do_splice_direct+0x177/0x240 fs/splice.c:1061
 do_sendfile+0x493/0xb20 fs/read_write.c:1444
 SYSC_sendfile64 fs/read_write.c:1505 [inline]
 SyS_sendfile64+0x11f/0x140 fs/read_write.c:1491
 do_syscall_64+0x19b/0x510 arch/x86/entry/common.c:292

Freed by task 14323:
 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
 do_exit+0x13b8/0x2960 kernel/exit.c:916

The buggy address belongs to the object at ffff888192254f00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 96 bytes inside of
 512-byte region [ffff888192254f00, ffff888192255100)
The buggy address belongs to the page:
page:ffffea0006489500 count:1 mapcount:0 mapping:          (null) index:0xffff888192255680 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 ffff888192255680 00000001000c0007
raw: ffffea00068a3220 ffffea00068778a0 ffff8881da802c00 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888192254e00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888192254e80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888192254f00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff888192254f80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888192255000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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