android_system_sepolicy/public/kernel.te
Sandeep Patil 34e35e9e95 Add label for kernel test files and executables
This required for kernel to do loopback mounts on filesystem
images created by the kernel system call tests in LTP.

Add a corresponding neverallow to stop all domains from accessing
the location at /data/local/tmp/ltp.

Bug: 73220071
Test: Boot sailfish successfully
Test: run vts-kernel -m VtsKernelLtp -t syscalls.fchown04

Change-Id: I73f5f14017e22971fc246a05751ba67be4653bca
Signed-off-by: Sandeep Patil <sspatil@google.com>
2018-02-22 12:55:30 -08:00

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# Life begins with the kernel.
type kernel, domain, mlstrustedsubject;
allow kernel self:global_capability_class_set sys_nice;
# Root fs.
r_dir_file(kernel, rootfs)
allow kernel 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: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:file read;
allow kernel asec_image_file:file read;
# Allow reading 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;
allow kernel nativetest_data_file:file read;
')
# 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;
###
### 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 };