NAME¶

kernel_selinux - Security Enhanced Linux Policy for the kernel processes

DESCRIPTION¶

Security-Enhanced Linux secures the kernel processes via flexible mandatory access control.

The kernel processes execute with the kernel_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.

For example:

ps -eZ | grep kernel_t

ENTRYPOINTS¶

The kernel_t SELinux type can be entered via the file_type, unlabeled_t, proc_type, filesystem_type, mtrr_device_t, sysctl_type file types.

The default entrypoint paths for the kernel_t domain are the following:

all files on the system, /dev/cpu/mtrr

PROCESS TYPES¶

SELinux defines process types (domains) for each process running on the system

You can see the context of a process using the -Z option to ps

Policy governs the access confined processes have to files. SELinux kernel policy is very flexible allowing users to setup their kernel processes in as secure a method as possible.

The following process types are defined for kernel:

kerneloops_t, kernel_t

Note: semanage permissive -a kernel_t can be used to make the process type kernel_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated.

BOOLEANS¶

SELinux policy is customizable based on least access required. kernel policy is extremely flexible and has several booleans that allow you to manipulate the policy and run kernel with the tightest access possible.

If you want to allow all domains to use other domains file descriptors, you must turn on the allow_domain_fd_use boolean. Enabled by default.

setsebool -P allow_domain_fd_use 1

If you want to allow unconfined executables to make their heap memory executable. Doing this is a really bad idea. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla, you must turn on the allow_execheap boolean. Disabled by default.

setsebool -P allow_execheap 1

If you want to allow unconfined executables to map a memory region as both executable and writable, this is dangerous and the executable should be reported in bugzilla), you must turn on the allow_execmem boolean. Enabled by default.

setsebool -P allow_execmem 1

If you want to allow all unconfined executables to use libraries requiring text relocation that are not labeled textrel_shlib_t), you must turn on the allow_execmod boolean. Enabled by default.

setsebool -P allow_execmod 1

If you want to allow unconfined executables to make their stack executable. This should never, ever be necessary. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla), you must turn on the allow_execstack boolean. Enabled by default.

setsebool -P allow_execstack 1

If you want to allow sysadm to debug or ptrace all processes, you must turn on the allow_ptrace boolean. Disabled by default.

setsebool -P allow_ptrace 1

If you want to allow system to run with NIS, you must turn on the allow_ypbind boolean. Disabled by default.

setsebool -P allow_ypbind 1

If you want to allow all domains to have the kernel load modules, you must turn on the domain_kernel_load_modules boolean. Disabled by default.

setsebool -P domain_kernel_load_modules 1

If you want to allow all domains to execute in fips_mode, you must turn on the fips_mode boolean. Enabled by default.

setsebool -P fips_mode 1

If you want to enable reading of urandom for all domains, you must turn on the global_ssp boolean. Disabled by default.

setsebool -P global_ssp 1

If you want to allow certain domains to map low memory in the kernel, you must turn on the mmap_low_allowed boolean. Disabled by default.

setsebool -P mmap_low_allowed 1

If you want to disable transitions to insmod, you must turn on the secure_mode_insmod boolean. Disabled by default.

setsebool -P secure_mode_insmod 1

If you want to boolean to determine whether the system permits loading policy, setting enforcing mode, and changing boolean values. Set this to true and you have to reboot to set it back, you must turn on the secure_mode_policyload boolean. Disabled by default.

setsebool -P secure_mode_policyload 1

If you want to support X userspace object manager, you must turn on the xserver_object_manager boolean. Disabled by default.

setsebool -P xserver_object_manager 1

MANAGED FILES¶

The SELinux process type kernel_t can manage files labeled with the following file types. The paths listed are the default paths for these file types. Note the processes UID still need to have DAC permissions.

file_type

all files on the system

FILE CONTEXTS¶

SELinux requires files to have an extended attribute to define the file type.

You can see the context of a file using the -Z option to ls

Policy governs the access confined processes have to these files. SELinux kernel policy is very flexible allowing users to setup their kernel processes in as secure a method as possible.

STANDARD FILE CONTEXT

SELinux defines the file context types for the kernel, if you wanted to store files with these types in a diffent paths, you need to execute the semanage command to sepecify alternate labeling and then use restorecon to put the labels on disk.

semanage fcontext -a -t kerneloops_tmp_t '/srv/mykernel_content(/.*)?'
restorecon -R -v /srv/mykernel_content

Note: SELinux often uses regular expressions to specify labels that match multiple files.

The following file types are defined for kernel:

kerneloops_exec_t

- Set files with the kerneloops_exec_t type, if you want to transition an executable to the kerneloops_t domain.

kerneloops_initrc_exec_t

- Set files with the kerneloops_initrc_exec_t type, if you want to transition an executable to the kerneloops_initrc_t domain.

kerneloops_tmp_t

- Set files with the kerneloops_tmp_t type, if you want to store kerneloops temporary files in the /tmp directories.

Note: File context can be temporarily modified with the chcon command. If you want to permanently change the file context you need to use the semanage fcontext command. This will modify the SELinux labeling database. You will need to use restorecon to apply the labels.

COMMANDS¶

semanage fcontext can also be used to manipulate default file context mappings.

semanage permissive can also be used to manipulate whether or not a process type is permissive.

semanage module can also be used to enable/disable/install/remove policy modules.

semanage boolean can also be used to manipulate the booleans

system-config-selinux is a GUI tool available to customize SELinux policy settings.

AUTHOR¶

This manual page was auto-generated using sepolicy manpage .

SEE ALSO¶

selinux(8), kernel(8), semanage(8), restorecon(8), chcon(1) , setsebool(8)