syzbot

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BUG: KCSAN: data-race in prepare_signal / vcpu_enter_guest

write to 0xffff8880a2118124 of 4 bytes by task 10730 on cpu 1:
 guest_exit_irqoff include/linux/context_tracking.h:153 [inline]
 vcpu_enter_guest+0xa54/0x3830 arch/x86/kvm/x86.c:8198
 vcpu_run arch/x86/kvm/x86.c:8291 [inline]
 kvm_arch_vcpu_ioctl_run+0x2a2/0xdc0 arch/x86/kvm/x86.c:8498
 kvm_vcpu_ioctl+0x752/0xa30 arch/x86/kvm/../../../virt/kvm/kvm_main.c:2772
 vfs_ioctl fs/ioctl.c:46 [inline]
 file_ioctl fs/ioctl.c:509 [inline]
 do_vfs_ioctl+0x991/0xc60 fs/ioctl.c:696
 ksys_ioctl+0xbd/0xe0 fs/ioctl.c:713
 __do_sys_ioctl fs/ioctl.c:720 [inline]
 __se_sys_ioctl fs/ioctl.c:718 [inline]
 __x64_sys_ioctl+0x4c/0x60 fs/ioctl.c:718
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880a2118124 of 4 bytes by task 10733 on cpu 0:
 sig_task_ignored kernel/signal.c:94 [inline]
 sig_ignored kernel/signal.c:119 [inline]
 prepare_signal+0x1f5/0x7a0 kernel/signal.c:956
 __send_signal+0x96/0x870 kernel/signal.c:1076
 send_signal+0x224/0x2b0 kernel/signal.c:1236
 do_send_sig_info+0x5f/0xc0 kernel/signal.c:1285
 do_send_specific+0xe7/0x110 kernel/signal.c:3775
 do_tkill+0xf7/0x130 kernel/signal.c:3801
 __do_sys_tkill kernel/signal.c:3836 [inline]
 __se_sys_tkill kernel/signal.c:3830 [inline]
 __x64_sys_tkill+0x50/0x70 kernel/signal.c:3830
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10733 Comm: syz-executor.3 Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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