Minimize public policy
Ideally, public should only contain APIs (types / attributes) for
vendor. The other statements like allow/neverallow/typeattributes are
regarded as implementation detail for platform and should be in private.
Bug: 232023812
Test: m selinux_policy
Test: diff <(git diff --staged | grep "^-" | cut -b2- | sort) \
<(git diff --staged | grep "^+" | cut -b2- | sort)
Test: remove comments on plat_sepolicy.cil, replace base_typeattr_*
to base_typeattr and then compare old and new plat_sepolicy.cil
Change-Id: I5e7d2da4465ab0216de6bacdf03077d37f6ffe12
diff --git a/private/kernel.te b/private/kernel.te
index 2d46b3e..1b82c66 100644
--- a/private/kernel.te
+++ b/private/kernel.te
@@ -32,6 +32,124 @@
allow kernel kmsg_device:chr_file write;
allow kernel gsid:fd use;
+allow kernel self:global_capability_class_set sys_nice;
+
+# Root fs.
+r_dir_file(kernel, rootfs)
+
+# Used to read androidboot.selinux property
+allow kernel {
+ proc_bootconfig
+ proc_cmdline
+}:file r_file_perms;
+
+# Get SELinux enforcing status.
+allow kernel selinuxfs:dir r_dir_perms;
+allow kernel selinuxfs:file r_file_perms;
+
+# Get file contexts during first stage
+allow kernel file_contexts_file:file r_file_perms;
+
+# Allow init relabel itself.
+allow kernel rootfs:file relabelfrom;
+allow kernel init_exec:file relabelto;
+# TODO: investigate why we need this.
+allow kernel init:process share;
+
+# cgroup filesystem initialization prior to setting the cgroup root directory label.
+allow kernel unlabeled:dir search;
+
+# Mount usbfs.
+allow kernel usbfs:filesystem mount;
+allow kernel usbfs:dir search;
+
+# 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;
+
+# Write to /proc/1/oom_adj prior to switching to init domain.
+allow kernel self:global_capability_class_set sys_resource;
+
+# Init reboot before switching selinux domains under certain error
+# conditions. Allow it.
+# As part of rebooting, init writes "u" to /proc/sysrq-trigger to
+# remount filesystems read-only. /data is not mounted at this point,
+# so we could ignore this. For now, we allow it.
+allow kernel self:global_capability_class_set sys_boot;
+allow kernel proc_sysrq:file w_file_perms;
+
+# Allow writing to /dev/kmsg which was created prior to loading policy.
+allow kernel tmpfs:chr_file write;
+
+# Set checkreqprot by init.rc prior to switching to init domain.
+allow kernel selinuxfs:file write;
+allow kernel self:security setcheckreqprot;
+
+# kernel thread "loop0", used by the loop block device, for ASECs (b/17158723)
+allow kernel { sdcard_type fuse }:file { read write };
+
+# f_mtp driver accesses files from kernel context.
+allow kernel mediaprovider:fd use;
+
+# 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 vold:fd use;
+allow kernel { app_data_file privapp_data_file }:file read;
+allow kernel asec_image_file:file read;
+
+# Allow mounting loop device in update_engine_unittests. (b/28319454)
+# and for LTP kernel tests (b/73220071)
+userdebug_or_eng(`
+ allow kernel update_engine_data_file:file { read write };
+ allow kernel nativetest_data_file:file { read write };
+')
+
+# Access to /data/media.
+# This should be removed if sdcardfs is modified to alter the secontext for its
+# accesses to the underlying FS.
+allow kernel media_rw_data_file:dir create_dir_perms;
+allow kernel media_rw_data_file:file create_file_perms;
+
+# Access to /data/misc/vold/virtual_disk.
+allow kernel vold_data_file:file { read write };
+
+# Allow the kernel to read APEX file descriptors and (staged) data files;
+# Needed because APEX uses the loopback driver, which issues requests from
+# a kernel thread in earlier kernel version.
+allow kernel apexd:fd use;
+allow kernel {
+ apex_data_file
+ staging_data_file
+ vendor_apex_file
+}:file read;
+# Also allow the kernel to read/write /data/local/tmp files via loop device
+# for ApexTestCases and fiemap_image_test.
+userdebug_or_eng(`
+ allow kernel shell_data_file:file { read write };
+')
+
+# Allow the first-stage init (which is running in the kernel domain) to execute the
+# dynamic linker when it re-executes /init to switch into the second stage.
+# Until Linux 4.8, the program interpreter (dynamic linker in this case) is executed
+# before the domain is switched to the target domain. So, we need to allow the kernel
+# domain (the source domain) to execute the dynamic linker (system_file type).
+# TODO(b/110147943) remove these allow rules when we no longer need to support Linux
+# kernel older than 4.8.
+allow kernel system_file:file execute;
+# The label for the dynamic linker is rootfs in the recovery partition. This is because
+# the recovery partition which is rootfs does not support xattr and thus labeling can't be
+# done at build-time. All files are by default labeled as rootfs upon booting.
+recovery_only(`
+ allow kernel rootfs:file execute;
+')
+
+# required by VTS lidbm unit test
+allow kernel appdomain_tmpfs:file { read write };
+
dontaudit kernel metadata_file:dir search;
dontaudit kernel ota_metadata_file:dir rw_dir_perms;
dontaudit kernel sysfs:dir r_dir_perms;
@@ -44,3 +162,29 @@
dontaudit kernel dm_user_device:chr_file { create setattr };
dontaudit kernel tmpfs:lnk_file read;
dontaudit kernel tmpfs:blk_file { open read };
+
+###
+### neverallow rules
+###
+
+# The initial task starts in the kernel domain (assigned via
+# initial_sid_contexts), but nothing ever transitions to it.
+neverallow * 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 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 { entrypoint execute_no_trans };
+
+# the kernel should not be accessing files owned by other users.
+# Instead of adding dac_{read_search,override}, fix the unix permissions
+# on files being accessed.
+neverallow kernel self:global_capability_class_set { dac_override dac_read_search };
+
+# Nobody should be ptracing kernel threads
+neverallow * kernel:process ptrace;