android_system_sepolicy/kernel.te

# Life begins with the kernel.
type kernel, domain;

# Run /init before we have switched domains.
allow kernel rootfs:file execute_no_trans;

# setcon to init domain.
allow kernel self:process setcurrent;
allow kernel init:process dyntransition;

# The kernel is unconfined.
unconfined_domain(kernel)

# cgroup filesystem initialization prior to setting the cgroup root directory label.
allow kernel unlabeled:dir search;

# Mount usbfs.
allow kernel usbfs:filesystem mount;

# init direct restorecon calls prior to switching to init domain
# /dev and /dev/socket
allow kernel { device socket_device }:dir relabelto;
# /dev/__properties__
allow kernel properties_device:file relabelto;
# /sys
allow kernel sysfs:{ dir file lnk_file } relabelfrom;
allow kernel sysfs_type:{ dir file lnk_file } relabelto;

# Initial setenforce by init prior to switching to init domain.
# We use dontaudit instead of allow to prevent a kernel spawned userspace
# process from turning off SELinux once enabled.
dontaudit kernel self:security setenforce;

# Set checkreqprot by init.rc prior to switching to init domain.
allow kernel self:security setcheckreqprot;

# MTP sync (b/15835289)
# kernel thread "loop0", used by the loop block device, for ASECs (b/17158723)
allow kernel sdcard_type:file { read write };

# Allow the kernel to read OBB files from app directories. (b/17428116)
# Kernel thread "loop0" reads a vold supplied file descriptor.
# Fixes CTS tests:
#  * android.os.storage.cts.StorageManagerTest#testMountAndUnmountObbNormal
#  * android.os.storage.cts.StorageManagerTest#testMountAndUnmountTwoObbs
allow kernel app_data_file:file read;

###
### neverallow rules
###

# The initial task starts in the kernel domain (assigned via
# initial_sid_contexts), but nothing ever transitions to it.
neverallow domain kernel:process { transition dyntransition };

# The kernel domain is never entered via an exec, nor should it
# ever execute a program outside the rootfs without changing to another domain.
# If you encounter an execute_no_trans denial on the kernel domain, then
# possible causes include:
# - The program is a kernel usermodehelper.  In this case, define a domain
#   for the program and domain_auto_trans() to it.
# - You failed to setcon u:r:init:s0 in your init.rc and thus your init
#   program was left in the kernel domain and is now trying to execute
#   some other program.  Fix your init.rc file.
# - You are running an exploit which switched to the init task credentials
#   and is then trying to exec a shell or other program.  You lose!
neverallow kernel { file_type fs_type -rootfs }:file { entrypoint execute_no_trans };