syzbot

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BUG: KCSAN: data-race in exit_signals / get_task_mm

read-write to 0xffff88800a875064 of 4 bytes by task 22460 on cpu 0:
 exit_signals+0x108/0x530 kernel/signal.c:2846
 do_exit+0x158/0x15a0 kernel/exit.c:762
 do_group_exit+0xa0/0x170 kernel/exit.c:903
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:914
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:912
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:912
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88800a875064 of 4 bytes by task 4886 on cpu 1:
 get_task_mm+0x3e/0x90 kernel/fork.c:1209
 get_task_cmdline fs/proc/base.c:348 [inline]
 proc_pid_cmdline_read+0x87/0x650 fs/proc/base.c:368
 vfs_read+0x154/0x5c0 fs/read_write.c:494
 ksys_read+0xce/0x180 fs/read_write.c:634
 __do_sys_read fs/read_write.c:644 [inline]
 __se_sys_read fs/read_write.c:642 [inline]
 __x64_sys_read+0x3e/0x50 fs/read_write.c:642
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 4886 Comm: systemd-journal Not tainted 5.10.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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