syzbot

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BUG: KCSAN: data-race in __send_signal / do_exit

write to 0xffff8880b236a0a4 of 4 bytes by task 14626 on cpu 1:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 exit_mm kernel/exit.c:471 [inline]
 do_exit+0x38d/0x18c0 kernel/exit.c:784
 do_group_exit+0xb4/0x1c0 kernel/exit.c:895
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x2f/0x6c0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:278 [inline]
 do_syscall_64+0x384/0x3a0 arch/x86/entry/common.c:304
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b236a0a4 of 4 bytes by task 14633 on cpu 0:
 __send_signal+0x2b4/0x870 kernel/signal.c:1093
 send_signal+0x224/0x2b0 kernel/signal.c:1236
 __group_send_sig_info kernel/signal.c:1275 [inline]
 do_notify_parent+0x55b/0x5e0 kernel/signal.c:1992
 exit_notify kernel/exit.c:670 [inline]
 do_exit+0x16ef/0x18c0 kernel/exit.c:818
 do_group_exit+0xb4/0x1c0 kernel/exit.c:895
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x2f/0x6c0 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode+0x1a6/0x1d0 arch/x86/entry/common.c:195
 swapgs_restore_regs_and_return_to_usermode+0x0/0x40

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 14633 Comm: syz-executor.1 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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