/sys/firmware/efi/vars/OsIndicationsSupported bug ?

I found /var/lib/dpkg/lock locked, so I looked for instances of apt through ps faux and found this:
[bash]
root 22549 0.0 0.0 4288 688 ? Ss 06:57 0:00 /bin/sh /usr/lib/apt/apt.systemd.daily install
root 22553 0.0 0.0 4288 1512 ? S 06:57 0:00 \_ /bin/sh /usr/lib/apt/apt.systemd.daily lock_is_held install
root 22584 0.0 0.5 156364 93128 ? S 06:57 0:15 \_ /usr/bin/python3 /usr/bin/unattended-upgrade
root 22592 0.0 0.5 158764 86188 ? S 06:57 0:04 \_ /usr/bin/python3 /usr/bin/unattended-upgrade
root 22735 0.0 0.0 23700 9044 pts/10 Ss+ 06:58 0:00 \_ /usr/bin/dpkg –status-fd 10 –configure –pending
root 22736 0.0 0.0 4288 724 pts/10 S+ 06:58 0:00 \_ /bin/sh -e /var/lib/dpkg/info/linux-image-4.9.0-6-amd64.postinst configure 4.9.82-1+deb9u3
root 22740 0.0 0.0 4184 1552 pts/10 S+ 06:58 0:00 \_ run-parts –report –exit-on-error –arg=4.9.0-6-amd64 –arg=/boot/vmlinuz-4.9.0-6-amd64 /etc/kernel/postinst.d
root 26294 0.0 0.0 4288 1616 pts/10 S+ 06:58 0:00 \_ /bin/sh /usr/sbin/grub-mkconfig -o /boot/grub/grub.cfg
root 28492 0.0 0.0 4288 724 pts/10 S+ 06:58 0:00 \_ /bin/sh /etc/grub.d/30_uefi-firmware
root 28494 0.0 0.0 4288 140 pts/10 S+ 06:58 0:00 \_ /bin/sh /etc/grub.d/30_uefi-firmware
root 28495 0.0 0.0 4288 144 pts/10 S+ 06:58 0:00 \_ /bin/sh /etc/grub.d/30_uefi-firmware
root 28496 0.0 0.0 5980 720 pts/10 S+ 06:58 0:00 \_ cat /sys/firmware/efi/vars/OsIndicationsSupported-8be4df61-93ca-11d2-aa0d-00e098032b8c/data
root 28497 0.0 0.0 5848 692 pts/10 S+ 06:58 0:00 \_ cut -b1
[/bash]

It seems that:
[bash]
cat /sys/firmware/efi/vars/OsIndicationsSupported-8be4df61-93ca-11d2-aa0d-00e098032b8c/data
[/bash]
was blocked, so I simply killed this cat process. I don’t know what went wrong.