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BUG: KCSAN: data-race in __run_timers / internal_add_timer

write to 0xffff888237c1b698 of 8 bytes by interrupt on cpu 1:
 enqueue_timer kernel/time/timer.c:597 [inline]
 internal_add_timer+0x140/0x260 kernel/time/timer.c:609
 add_timer_on+0x262/0x2a0 kernel/time/timer.c:1180
 clocksource_watchdog+0x710/0x750 kernel/time/clocksource.c:303
 call_timer_fn+0x2e/0x1d0 kernel/time/timer.c:1431
 expire_timers+0x135/0x250 kernel/time/timer.c:1476
 __run_timers+0x358/0x420 kernel/time/timer.c:1745
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1758
 __do_softirq+0x12c/0x275 kernel/softirq.c:559
 invoke_softirq kernel/softirq.c:433 [inline]
 __irq_exit_rcu+0xa5/0xb0 kernel/softirq.c:637
 sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
 iov_iter_init lib/iov_iter.c:493 [inline]
 __import_iovec+0x194/0x270 lib/iov_iter.c:2049
 import_iovec+0x69/0x80 lib/iov_iter.c:2083
 copy_msghdr_from_user net/socket.c:2288 [inline]
 recvmsg_copy_msghdr net/socket.c:2535 [inline]
 ___sys_recvmsg net/socket.c:2607 [inline]
 do_recvmmsg+0x67b/0x9e0 net/socket.c:2705
 __sys_recvmmsg net/socket.c:2784 [inline]
 __do_sys_recvmmsg net/socket.c:2807 [inline]
 __se_sys_recvmmsg net/socket.c:2800 [inline]
 __x64_sys_recvmmsg+0xcf/0x150 net/socket.c:2800
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237c1b698 of 8 bytes by interrupt on cpu 0:
 __run_timers+0x50/0x420 kernel/time/timer.c:1726
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1758
 __do_softirq+0x12c/0x275 kernel/softirq.c:559
 invoke_softirq kernel/softirq.c:433 [inline]
 __irq_exit_rcu+0xa5/0xb0 kernel/softirq.c:637
 sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
 should_watch kernel/kcsan/core.c:269 [inline]
 check_access kernel/kcsan/core.c:632 [inline]
 __tsan_read8+0x150/0x180 kernel/kcsan/core.c:845
 __import_iovec+0x1ed/0x270 lib/iov_iter.c:2050
 import_iovec+0x69/0x80 lib/iov_iter.c:2083
 copy_msghdr_from_user net/socket.c:2288 [inline]
 recvmsg_copy_msghdr net/socket.c:2535 [inline]
 ___sys_recvmsg net/socket.c:2607 [inline]
 do_recvmmsg+0x67b/0x9e0 net/socket.c:2705
 __sys_recvmmsg net/socket.c:2784 [inline]
 __do_sys_recvmmsg net/socket.c:2807 [inline]
 __se_sys_recvmmsg net/socket.c:2800 [inline]
 __x64_sys_recvmmsg+0xcf/0x150 net/socket.c:2800
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7398 Comm: syz-executor.1 Not tainted 5.12.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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