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BUG: KCSAN: data-race in complete_signal / handle_mm_fault

read to 0xffff8880a9924090 of 8 bytes by interrupt on cpu 0:
 wants_signal kernel/signal.c:978 [inline]
 complete_signal+0xcd/0x5e0 kernel/signal.c:995
 send_sigqueue+0x2cf/0x4b0 kernel/signal.c:1879
 posix_timer_event kernel/time/posix-timers.c:328 [inline]
 posix_timer_fn+0x10d/0x230 kernel/time/posix-timers.c:354
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x274/0x5f0 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x22a/0x480 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1110 [inline]
 smp_apic_timer_interrupt+0xdc/0x280 arch/x86/kernel/apic/apic.c:1135
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 is_atomic kernel/kcsan/core.c:174 [inline]
 should_watch kernel/kcsan/core.c:203 [inline]
 check_access kernel/kcsan/core.c:458 [inline]
 __tsan_unaligned_write8+0x88/0x110 kernel/kcsan/core.c:589
 sock_alloc_inode+0xd7/0x100 net/socket.c:251
 alloc_inode+0x48/0x130 fs/inode.c:230
 new_inode_pseudo+0x35/0xe0 fs/inode.c:919
 sock_alloc+0x40/0x110 net/socket.c:560
 __sys_accept4_file+0xdf/0x360 net/socket.c:1715
 __sys_accept4+0x63/0xb0 net/socket.c:1796
 __do_sys_accept net/socket.c:1814 [inline]
 __se_sys_accept net/socket.c:1811 [inline]
 __x64_sys_accept+0x4e/0x60 net/socket.c:1811
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

write to 0xffff8880a9924090 of 8 bytes by task 13159 on cpu 1:
 handle_mm_fault+0x4a/0x530 mm/memory.c:4089
 do_user_addr_fault arch/x86/mm/fault.c:1441 [inline]
 __do_page_fault+0x456/0x8d0 arch/x86/mm/fault.c:1506
 do_page_fault+0x38/0x194 arch/x86/mm/fault.c:1530
 page_fault+0x34/0x40 arch/x86/entry/entry_64.S:1203

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13159 Comm: syz-executor.3 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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