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BUG: KCSAN: data-race in add_timer / run_timer_softirq

write to 0xffff88812c11dc88 of 8 bytes by interrupt on cpu 1:
 expire_timers kernel/time/timer.c:1446 [inline]
 __run_timers kernel/time/timer.c:1774 [inline]
 __run_timers kernel/time/timer.c:1741 [inline]
 run_timer_softirq+0x440/0xbd0 kernel/time/timer.c:1787
 __do_softirq+0x118/0x34a kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xb5/0xd0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:546 [inline]
 smp_apic_timer_interrupt+0xe2/0x270 arch/x86/kernel/apic/apic.c:1140
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 arch_local_irq_restore arch/x86/include/asm/paravirt.h:759 [inline]
 kcsan_setup_watchpoint+0x25a/0x440 kernel/kcsan/core.c:542
 pte_val arch/x86/include/asm/paravirt.h:385 [inline]
 pte_pfn arch/x86/include/asm/pgtable.h:215 [inline]
 vm_normal_page+0x2c/0x220 mm/memory.c:595
 zap_pte_range mm/memory.c:1065 [inline]
 zap_pmd_range mm/memory.c:1196 [inline]
 zap_pud_range mm/memory.c:1225 [inline]
 zap_p4d_range mm/memory.c:1246 [inline]
 unmap_page_range+0x7ff/0x1c50 mm/memory.c:1267
 unmap_single_vma+0x13c/0x1f0 mm/memory.c:1312
 unmap_vmas+0xe2/0x1b0 mm/memory.c:1344
 exit_mmap+0x13e/0x2f0 mm/mmap.c:3150
 __mmput kernel/fork.c:1085 [inline]
 mmput+0xe2/0x260 kernel/fork.c:1106
 exit_mm kernel/exit.c:479 [inline]
 do_exit+0x644/0x11e0 kernel/exit.c:782
 do_group_exit+0xae/0x1a0 kernel/exit.c:893
 get_signal+0x2a7/0x1290 kernel/signal.c:2739
 do_signal+0x2b/0x840 arch/x86/kernel/signal.c:784
 exit_to_usermode_loop+0x24a/0x2c0 arch/x86/entry/common.c:161
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812c11dc88 of 8 bytes by task 22929 on cpu 0:
 __mod_timer kernel/time/timer.c:1027 [inline]
 add_timer+0x175/0x550 kernel/time/timer.c:1137
 __queue_delayed_work+0x13c/0x1d0 kernel/workqueue.c:1648
 queue_delayed_work_on+0xef/0x110 kernel/workqueue.c:1673
 queue_delayed_work include/linux/workqueue.h:522 [inline]
 schedule_delayed_work include/linux/workqueue.h:626 [inline]
 fput_many+0x119/0x130 fs/file_table.c:351
 fput+0x20/0x30 fs/file_table.c:357
 path_openat+0x1aae/0x23d0 fs/namei.c:3355
 do_filp_open+0x11e/0x1b0 fs/namei.c:3373
 do_open_execat+0x117/0x420 fs/exec.c:860
 __do_execve_file.isra.0+0xda0/0x1120 fs/exec.c:1821
 do_execveat_common fs/exec.c:1927 [inline]
 do_execve+0x39/0x50 fs/exec.c:1944
 call_usermodehelper_exec_async+0x394/0x3e0 kernel/umh.c:112
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 22929 Comm: kworker/u4:1 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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