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1.1.1.2 Ensure freevxfs kernel module is not available

Information

The freevxfs filesystem type is a free version of the Veritas type filesystem. This is the primary filesystem type for HP-UX operating systems.

Removing support for unneeded filesystem types reduces the local attack surface of the system. If this filesystem type is not needed, disable it.

Solution

Run the following to unload and disable the freevxfs kernel module. This can also be done by running the script included below.

Run the following commands to unload the freevxfs kernel module:

# modprobe -r freevxfs 2>/dev/null
# rmmod freevxfs 2>/dev/null

Perform the following to disable the freevxfs kernel module:

Create a file ending inconf with install freevxfs /bin/false in the /etc/modprobe.d/ directory

Example:

# printf '\n%s\n' "install freevxfs /bin/false" >> freevxfs.conf

Create a file ending inconf with blacklist freevxfs in the /etc/modprobe.d/ directory

Example:

# printf '\n%s\n' "blacklist freevxfs" >> freevxfs.conf

Optional remediation script:

This script will perform the above remediation as required by the system

#!/usr/bin/env bash

{
 a_output2=() a_output3=() l_dl="" l_mod_name="freevxfs" l_mod_type="fs"
 l_mod_path="$(readlink -f /usr/lib/modules/**/kernel/$l_mod_type || readlink -f /lib/modules/**/kernel/$l_mod_type)"
 f_module_fix()
 {
 l_dl="y" a_showconfig=()
 while IFS= read -r l_showconfig; do
 a_showconfig+=("$l_showconfig")
 done < <(modprobe --showconfig | grep -P -- '\b(install|blacklist)\h+'"${l_mod_chk_name//-/_}"'\b')
 if lsmod | grep "$l_mod_chk_name" &> /dev/null; then
 a_output2+=(" - unloading kernel module: \"$l_mod_name\"")
 modprobe -r "$l_mod_chk_name" 2>/dev/null; rmmod "$l_mod_name" 2>/dev/null
 fi
 if ! grep -Pq -- '\binstall\h+'"${l_mod_chk_name//-/_}"'\h+(\/usr)?\/bin\/(true|false)\b' <<< "${a_showconfig[*]}"; then
 a_output2+=(" - setting kernel module: \"$l_mod_name\" to \"$(readlink -f /bin/false)\"")
 printf '%s\n' "install $l_mod_chk_name $(readlink -f /bin/false)" >> /etc/modprobe.d/"$l_mod_name".conf
 fi
 if ! grep -Pq -- '\bblacklist\h+'"${l_mod_chk_name//-/_}"'\b' <<< "${a_showconfig[*]}"; then
 a_output2+=(" - denylisting kernel module: \"$l_mod_name\"")
 printf '%s\n' "blacklist $l_mod_chk_name" >> /etc/modprobe.d/"$l_mod_name".conf
 fi
 }
 for l_mod_base_directory in $l_mod_path; do # Check if the module exists on the system
 if [ -d "$l_mod_base_directory/${l_mod_name/-/\/}" ] && [ -n "$(ls -A "$l_mod_base_directory/${l_mod_name/-/\/}")" ]; then
 a_output3+=(" - \"$l_mod_base_directory\"")
 l_mod_chk_name="$l_mod_name"
 [[ "$l_mod_name" =~ overlay ]] && l_mod_chk_name="${l_mod_name::-2}"
 [ "$l_dl" != "y" ] && f_module_fix
 else
 printf '%s\n' " - kernel module: \"$l_mod_name\" doesn't exist in \"$l_mod_base_directory\""
 fi
 done
 [ "${#a_output3[@]}" -gt 0 ] && printf '%s\n' "" " -- INFO --" " - module: \"$l_mod_name\" exists in:" "${a_output3[@]}"
 [ "${#a_output2[@]}" -gt 0 ] && printf '%s\n' "" "${a_output2[@]}" || printf '%s\n' "" " - No changes needed"
 printf '%s\n' "" " - remediation of kernel module: \"$l_mod_name\" complete" ""
}

See Also

https://workbench.cisecurity.org/benchmarks/21095

Item Details

Category: CONFIGURATION MANAGEMENT

References: 800-53|CM-6, 800-53|CM-7, CSCv7|9.2

Plugin: Unix

Control ID: 95922b23591979e725384ea6714f7e5f8bb29257e2a9b9962df055b8bc8c5c38