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BUG: KASAN: use-after-free in atomic_dec_and_test include/asm-generic/atomic-instrumented.h:222 [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+0x48d/0x1440 kernel/events/core.c:4451
Write of size 4 at addr ffff8801948e6720 by task syz-executor6/10444

CPU: 1 PID: 10444 Comm: syz-executor6 Not tainted 4.18.0-rc4+ #50
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
 print_address_description+0x6c/0x20b mm/kasan/report.c:256
 kasan_report_error mm/kasan/report.c:354 [inline]
 kasan_report.cold.7+0x242/0x2fe 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:222 [inline]
 put_task_struct include/linux/sched/task.h:95 [inline]
 _free_event+0x48d/0x1440 kernel/events/core.c:4451
 free_event+0xb4/0x180 kernel/events/core.c:4472
 perf_event_release_kernel+0x7d5/0x1050 kernel/events/core.c:4633
 perf_release+0x37/0x50 kernel/events/core.c:4647
 __fput+0x355/0x8b0 fs/file_table.c:209
 ____fput+0x15/0x20 fs/file_table.c:243
 task_work_run+0x1ec/0x2a0 kernel/task_work.c:113
 tracehook_notify_resume include/linux/tracehook.h:192 [inline]
 exit_to_usermode_loop+0x313/0x370 arch/x86/entry/common.c:166
 prepare_exit_to_usermode arch/x86/entry/common.c:197 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:268 [inline]
 do_syscall_32_irqs_on arch/x86/entry/common.c:341 [inline]
 do_fast_syscall_32+0xcd5/0xfb2 arch/x86/entry/common.c:397
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f27cb9
Code: 55 08 8b 88 64 cd ff ff 8b 98 68 cd ff ff 89 c8 85 d2 74 02 89 0a 5b 5d c3 8b 04 24 c3 8b 1c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90 90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90 
RSP: 002b:000000000845eacc EFLAGS: 00000216 ORIG_RAX: 0000000000000006
RAX: 0000000000000000 RBX: 0000000000000017 RCX: 0000000000000000
RDX: 0000000000000018 RSI: 000000000845eb1c RDI: 000000000845f7ac
RBP: 000000000845f188 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Allocated by task 10447:
 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+0x144/0x780 mm/slab.c:3644
 alloc_task_struct_node kernel/fork.c:157 [inline]
 dup_task_struct kernel/fork.c:779 [inline]
 copy_process.part.39+0x16b5/0x7220 kernel/fork.c:1641
 copy_process kernel/fork.c:1616 [inline]
 _do_fork+0x291/0x12a0 kernel/fork.c:2099
 __do_compat_sys_x86_clone arch/x86/ia32/sys_ia32.c:240 [inline]
 __se_compat_sys_x86_clone arch/x86/ia32/sys_ia32.c:236 [inline]
 __ia32_compat_sys_x86_clone+0xbc/0x140 arch/x86/ia32/sys_ia32.c:236
 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
 do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

Freed by task 10447:
 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+0x86/0x2d0 mm/slab.c:3756
 free_task_struct kernel/fork.c:162 [inline]
 free_task+0x16e/0x1f0 kernel/fork.c:390
 copy_process.part.39+0x15c9/0x7220 kernel/fork.c:2034
 copy_process kernel/fork.c:1616 [inline]
 _do_fork+0x291/0x12a0 kernel/fork.c:2099
 __do_compat_sys_x86_clone arch/x86/ia32/sys_ia32.c:240 [inline]
 __se_compat_sys_x86_clone arch/x86/ia32/sys_ia32.c:236 [inline]
 __ia32_compat_sys_x86_clone+0xbc/0x140 arch/x86/ia32/sys_ia32.c:236
 do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
 do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397
 entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139

The buggy address belongs to the object at ffff8801948e6700
 which belongs to the cache task_struct(65:syz6) of size 5952
The buggy address is located 32 bytes inside of
 5952-byte region [ffff8801948e6700, ffff8801948e7e40)
The buggy address belongs to the page:
page:ffffea0006523980 count:1 mapcount:0 mapping:ffff8801b0500900 index:0x0 compound_mapcount: 0
flags: 0x2fffc0000008100(slab|head)
raw: 02fffc0000008100 ffffea0006ac5088 ffff8801aae1de48 ffff8801b0500900
raw: 0000000000000000 ffff8801948e6700 0000000100000001 ffff8801b85323c0
page dumped because: kasan: bad access detected
page->mem_cgroup:ffff8801b85323c0

Memory state around the buggy address:
 ffff8801948e6600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff8801948e6680: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff8801948e6700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff8801948e6780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8801948e6800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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