Detections
Analytics
1.1.1.3 Ensure mounting of jffs2 filesystems is disabled
Information
The jffs2 (journaling flash filesystem 2) filesystem type is a log-structured filesystem used in flash memory devices.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 script to disable the jffs2 module:If the module is available in the running kernel:
- Create a file with install jffs2 /bin/false in the /etc/modprobe.d/ directory
- Create a file with blacklist jffs2 in the /etc/modprobe.d/ directory
- Unload jffs2 from the kernel
If available in ANY installed kernel:
- Create a file with blacklist jffs2 in the /etc/modprobe.d/ directory
If the kernel module is not available on the system or pre-compiled into the kernel:
- No remediation is necessary
#!/usr/bin/env bash
{
l_mname="jffs2" # set module name
l_mtype="fs" # set module type
l_mpath="/lib/modules/**/kernel/$l_mtype"
l_mpname="$(tr '-' '_' <<< "$l_mname")"
l_mndir="$(tr '-' '/' <<< "$l_mname")"
module_loadable_fix()
{
# If the module is currently loadable, add "install {MODULE_NAME} /bin/false" to a file in "/etc/modprobe.d"
l_loadable="$(modprobe -n -v "$l_mname")"
[ "$(wc -l <<< "$l_loadable")" -gt "1" ] && l_loadable="$(grep -P -- "(^h*install|b$l_mname)b" <<< "$l_loadable")"
if ! grep -Pq -- '^h*install /bin/(true|false)' <<< "$l_loadable"; then
echo -e "
- setting module: \"$l_mname\" to be not loadable"
echo -e "install $l_mname /bin/false" >> /etc/modprobe.d/"$l_mpname".conf
fi
}
module_loaded_fix()
{
# If the module is currently loaded, unload the module
if lsmod | grep "$l_mname" > /dev/null 2>&1; then
echo -e "
- unloading module \"$l_mname\""
modprobe -r "$l_mname"
fi
}
module_deny_fix()
{
# If the module isn't deny listed, denylist the module
if ! modprobe --showconfig | grep -Pq -- "^h*blacklisth+$l_mpnameb"; then
echo -e "
- deny listing \"$l_mname\""
echo -e "blacklist $l_mname" >> /etc/modprobe.d/"$l_mpname".conf
fi
}
# Check if the module exists on the system
for l_mdir in $l_mpath; do
if [ -d "$l_mdir/$l_mndir" ] && [ -n "$(ls -A $l_mdir/$l_mndir)" ]; then
echo -e "
- module: \"$l_mname\" exists in \"$l_mdir\"
- checking if disabled..."
module_deny_fix
if [ "$l_mdir" = "/lib/modules/$(uname -r)/kernel/$l_mtype" ]; then
module_loadable_fix
module_loaded_fix
fi
else
echo -e "
- module: \"$l_mname\" doesn't exist in \"$l_mdir\"
"
fi
done
echo -e "
- remediation of module: \"$l_mname\" complete
"
}
See Also
Item Details
Audit Name: CIS Ubuntu Linux 20.04 LTS Server L1 v2.0.1
Category: CONFIGURATION MANAGEMENT
References: 800-53|CM-6, 800-53|CM-7, CSCv7|9.2
Plugin: Unix
Control ID: cb80e36e5a1d48acd57d577dd0e33b47cde2ccae5eafd3dc62be420c7f2d4668