/etc/sysctl.d/10-kernel-hardening.conf is in procps 1:3.3.9-1ubuntu2.3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | # These settings are specific to hardening the kernel itself from attack
# from userspace, rather than protecting userspace from other malicious
# userspace things.
#
#
# When an attacker is trying to exploit the local kernel, it is often
# helpful to be able to examine where in memory the kernel, modules,
# and data structures live. As such, kernel addresses should be treated
# as sensitive information.
#
# Many files and interfaces contain these addresses (e.g. /proc/kallsyms,
# /proc/modules, etc), and this setting can censor the addresses. A value
# of "0" allows all users to see the kernel addresses. A value of "1"
# limits visibility to the root user, and "2" blocks even the root user.
kernel.kptr_restrict = 1
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