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BUG: KCSAN: data-race in complete_signal / do_signal_stop

write to 0xffff8880341a5024 of 4 bytes by task 1923 on cpu 1:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 do_signal_stop+0x562/0x6d0 kernel/signal.c:2395
 get_signal+0x6e4/0x1650 kernel/signal.c:2717
 arch_do_signal+0x25/0x270 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:159 [inline]
 exit_to_user_mode_prepare+0x124/0x210 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:265
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880341a5024 of 4 bytes by interrupt on cpu 0:
 wants_signal kernel/signal.c:977 [inline]
 complete_signal+0x7c/0x600 kernel/signal.c:1000
 send_sigqueue+0x261/0x450 kernel/signal.c:1880
 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:1524
 __hrtimer_run_queues kernel/time/hrtimer.c:1588 [inline]
 hrtimer_interrupt+0x37c/0xa40 kernel/time/hrtimer.c:1650
 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:706
 __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:581
 console_unlock+0x8ed/0xab0 arch/x86/include/asm/paravirt.h:770
 vprintk_emit+0x37f/0x4f0 kernel/printk/printk.c:2029
 vprintk_default+0x24/0x30 kernel/printk/printk.c:2047
 vprintk_func+0x13d/0x140 kernel/printk/printk_safe.c:393
 printk+0x62/0x82 kernel/printk/printk.c:2078
 ubifs_mount+0x839/0x3300 fs/ubifs/super.c:2259
 legacy_get_tree+0x70/0xc0 fs/fs_context.c:592
 vfs_get_tree+0x4d/0x1a0 fs/super.c:1547
 do_new_mount fs/namespace.c:2875 [inline]
 path_mount+0x118d/0x1c70 fs/namespace.c:3192
 do_mount fs/namespace.c:3205 [inline]
 __do_sys_mount fs/namespace.c:3413 [inline]
 __se_sys_mount+0x126/0x180 fs/namespace.c:3390
 __x64_sys_mount+0x63/0x70 fs/namespace.c:3390
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1949 Comm: syz-executor.4 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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