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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 ffff8881c4397960 by task syz-executor.5/16800

CPU: 0 PID: 16800 Comm: syz-executor.5 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 16802:
 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_perf_context+0x44/0xe0 kernel/events/core.c:3864
 find_get_context.isra.0+0x119/0x550 kernel/events/core.c:3953
 SYSC_perf_event_open kernel/events/core.c:10160 [inline]
 SyS_perf_event_open+0x9d3/0x2530 kernel/events/core.c:9988
 do_syscall_64+0x19b/0x510 arch/x86/entry/common.c:292

Freed by task 74:
 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
 __rcu_reclaim kernel/rcu/rcu.h:195 [inline]
 rcu_do_batch kernel/rcu/tree.c:2699 [inline]
 invoke_rcu_callbacks kernel/rcu/tree.c:2962 [inline]
 __rcu_process_callbacks kernel/rcu/tree.c:2929 [inline]
 rcu_process_callbacks+0x56f/0xf40 kernel/rcu/tree.c:2946
 __do_softirq+0x234/0x9ca kernel/softirq.c:288

The buggy address belongs to the object at ffff8881c4397900
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 96 bytes inside of
 512-byte region [ffff8881c4397900, ffff8881c4397b00)
The buggy address belongs to the page:
page:ffffea000710e580 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
flags: 0x4000000000010200(slab|head)
raw: 4000000000010200 0000000000000000 0000000000000000 00000001000c000c
raw: dead000000000100 dead000000000200 ffff8881d6402c00 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff8881c4397800: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8881c4397880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8881c4397900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff8881c4397980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8881c4397a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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