syzbot

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BUG: KCSAN: data-race in exit_signals / get_task_mm

write to 0xffff888126a8e02c of 4 bytes by task 27875 on cpu 1:
 exit_signals+0xe1/0x4a0 kernel/signal.c:2927
 do_exit+0x194/0x1560 kernel/exit.c:782
 do_group_exit+0xa4/0x1a0 kernel/exit.c:923
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:934
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:932
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:932
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888126a8e02c of 4 bytes by task 1025 on cpu 0:
 get_task_mm+0x3e/0xb0 kernel/fork.c:1226
 proc_pid_status+0x35/0x13c0 fs/proc/array.c:439
 proc_single_show+0x84/0x100 fs/proc/base.c:774
 seq_read_iter+0x2ef/0x910 fs/seq_file.c:227
 seq_read+0x221/0x260 fs/seq_file.c:159
 vfs_read+0x154/0x5d0 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+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 1025 Comm: systemd-journal Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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