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BUG: KCSAN: data-race in do_notify_parent_cldstop / prepare_signal

write to 0xffff88809bda65e0 of 4 bytes by interrupt on cpu 0:
 prepare_signal+0xd21/0xdb0 kernel/signal.c:957
 send_sigqueue+0xea/0x450 kernel/signal.c:1860
 posix_timer_event kernel/time/posix-timers.c:354 [inline]
 posix_timer_fn+0xe8/0x210 kernel/time/posix-timers.c:380
 __run_hrtimer+0x154/0x4b0 kernel/time/hrtimer.c:1520
 __hrtimer_run_queues kernel/time/hrtimer.c:1584 [inline]
 hrtimer_interrupt+0x37c/0xa40 kernel/time/hrtimer.c:1646
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0xa3/0x280 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0x80/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:596
 tomoyo_check_path_acl+0x3/0xe0 security/tomoyo/file.c:254
 tomoyo_check_acl+0xcc/0x220 security/tomoyo/domain.c:175
 tomoyo_path_permission security/tomoyo/file.c:586 [inline]
 tomoyo_path_perm+0x22f/0x330 security/tomoyo/file.c:838
 tomoyo_inode_getattr+0x18/0x20 security/tomoyo/tomoyo.c:123
 security_inode_getattr+0x7f/0xd0 security/security.c:1278
 vfs_getattr fs/stat.c:121 [inline]
 vfs_statx_fd fs/stat.c:151 [inline]
 vfs_fstat include/linux/fs.h:3312 [inline]
 __do_sys_newfstat fs/stat.c:398 [inline]
 __se_sys_newfstat+0x5a/0x510 fs/stat.c:395
 __x64_sys_newfstat+0x2d/0x40 fs/stat.c:395
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809bda65e0 of 4 bytes by task 24512 on cpu 1:
 do_notify_parent_cldstop+0x1b2/0x280 kernel/signal.c:2057
 do_signal_stop+0x505/0x6d0 kernel/signal.c:2389
 get_signal+0x78d/0x1520 kernel/signal.c:2597
 do_signal+0x25/0x270 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:212 [inline]
 __prepare_exit_to_usermode+0x127/0x230 arch/x86/entry/common.c:246
 __syscall_return_slowpath+0x47/0x60 arch/x86/entry/common.c:329
 do_syscall_64+0x5d/0xb0 arch/x86/entry/common.c:368
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 24512 Comm: syz-executor.0 Not tainted 5.8.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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