1# Life begins with the kernel.
2type kernel, domain, mlstrustedsubject;
3
4allow kernel self:capability sys_nice;
5
6# Allow init relabel itself.
7allow kernel rootfs:file relabelfrom;
8allow kernel init_exec:file relabelto;
9# TODO: investigate why we need this.
10allow kernel init:process share;
11
12# cgroup filesystem initialization prior to setting the cgroup root directory label.
13allow kernel unlabeled:dir search;
14
15# Mount usbfs.
16allow kernel usbfs:filesystem mount;
17allow kernel usbfs:dir search;
18
19# Initial setenforce by init prior to switching to init domain.
20# We use dontaudit instead of allow to prevent a kernel spawned userspace
21# process from turning off SELinux once enabled.
22dontaudit kernel self:security setenforce;
23
24# Write to /proc/1/oom_adj prior to switching to init domain.
25allow kernel self:capability sys_resource;
26
27# Init reboot before switching selinux domains under certain error
28# conditions. Allow it.
29# As part of rebooting, init writes "u" to /proc/sysrq-trigger to
30# remount filesystems read-only. /data is not mounted at this point,
31# so we could ignore this. For now, we allow it.
32allow kernel self:capability sys_boot;
33allow kernel proc_sysrq:file w_file_perms;
34
35# Allow writing to /dev/__kmsg__ which was created prior to
36# loading policy
37allow kernel tmpfs:chr_file write;
38
39# Set checkreqprot by init.rc prior to switching to init domain.
40allow kernel selinuxfs:file write;
41allow kernel self:security setcheckreqprot;
42
43# MTP sync (b/15835289)
44# kernel thread "loop0", used by the loop block device, for ASECs (b/17158723)
45allow kernel untrusted_app:fd use;
46allow kernel sdcard_type:file { read write };
47
48# Allow the kernel to read OBB files from app directories. (b/17428116)
49# Kernel thread "loop0" reads a vold supplied file descriptor.
50# Fixes CTS tests:
51#  * android.os.storage.cts.StorageManagerTest#testMountAndUnmountObbNormal
52#  * android.os.storage.cts.StorageManagerTest#testMountAndUnmountTwoObbs
53allow kernel vold:fd use;
54allow kernel app_data_file:file read;
55allow kernel asec_image_file:file read;
56
57domain_auto_trans(kernel, init_exec, init)
58
59###
60### neverallow rules
61###
62
63# The initial task starts in the kernel domain (assigned via
64# initial_sid_contexts), but nothing ever transitions to it.
65neverallow domain kernel:process { transition dyntransition };
66
67# The kernel domain is never entered via an exec, nor should it
68# ever execute a program outside the rootfs without changing to another domain.
69# If you encounter an execute_no_trans denial on the kernel domain, then
70# possible causes include:
71# - The program is a kernel usermodehelper.  In this case, define a domain
72#   for the program and domain_auto_trans() to it.
73# - You failed to setcon u:r:init:s0 in your init.rc and thus your init
74#   program was left in the kernel domain and is now trying to execute
75#   some other program.  Fix your init.rc file.
76# - You are running an exploit which switched to the init task credentials
77#   and is then trying to exec a shell or other program.  You lose!
78neverallow kernel { file_type fs_type -rootfs }:file { entrypoint execute_no_trans };
79