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BUG: KCSAN: data-race in perf_event_update_userpage / perf_event_update_userpage

write to 0xffff8881409ef008 of 4 bytes by task 9533 on cpu 0:
 perf_event_update_userpage+0x2d0/0x2f0 kernel/events/core.c:5852
 cpu_clock_event_add+0x11d/0x130 kernel/events/core.c:10638
 event_sched_in+0x761/0xdd0 kernel/events/core.c:2559
 group_sched_in kernel/events/core.c:2595 [inline]
 merge_sched_in kernel/events/core.c:3723 [inline]
 visit_groups_merge+0x84b/0x15e0 kernel/events/core.c:3696
 ctx_flexible_sched_in kernel/events/core.c:3764 [inline]
 ctx_sched_in+0x1db/0x200 kernel/events/core.c:3809
 perf_event_sched_in kernel/events/core.c:3818 [inline]
 ctx_resched+0x193/0x210 kernel/events/core.c:2749
 __perf_install_in_context+0x1f0/0x280 kernel/events/core.c:2817
 remote_function+0x97/0xb0 kernel/events/core.c:91
 generic_exec_single+0xa6/0x1f0 kernel/smp.c:518
 smp_call_function_single+0x138/0x2a0 kernel/smp.c:755
 task_function_call kernel/events/core.c:119 [inline]
 perf_install_in_context+0x2fe/0x540 kernel/events/core.c:2918
 __do_sys_perf_event_open kernel/events/core.c:12352 [inline]
 __se_sys_perf_event_open+0x1c78/0x27f0 kernel/events/core.c:11960
 __x64_sys_perf_event_open+0x63/0x70 kernel/events/core.c:11960
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881409ef008 of 4 bytes by task 9590 on cpu 1:
 perf_event_update_userpage+0x13b/0x2f0 kernel/events/core.c:5836
 perf_mmap+0xb6f/0xce0 kernel/events/core.c:6315
 call_mmap include/linux/fs.h:2119 [inline]
 mmap_region+0xbcb/0x1400 mm/mmap.c:1808
 do_mmap+0x73f/0xc40 mm/mmap.c:1584
 vm_mmap_pgoff+0xf9/0x1d0 mm/util.c:519
 ksys_mmap_pgoff+0x2a8/0x380 mm/mmap.c:1635
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000001 -> 0x00000002

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9590 Comm: syz-executor.3 Tainted: G        W         5.14.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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