public/system_server.te

#
# System Server aka system_server spawned by zygote.
# Most of the framework services run in this process.
#
type system_server, domain, domain_deprecated, mlstrustedsubject;

# For art.
allow system_server dalvikcache_data_file:dir r_dir_perms;
allow system_server dalvikcache_data_file:file { r_file_perms execute };

# Enable system server to check the foreign dex usage markers.
# We need search on top level directories so that we can get to the files
allow system_server user_profile_data_file:dir search;
allow system_server user_profile_data_file:file getattr;
allow system_server user_profile_foreign_dex_data_file:dir { add_name open read write search remove_name };
allow system_server user_profile_foreign_dex_data_file:file { getattr rename unlink };

# /data/resource-cache
allow system_server resourcecache_data_file:file r_file_perms;
allow system_server resourcecache_data_file:dir r_dir_perms;

# ptrace to processes in the same domain for debugging crashes.
allow system_server self:process ptrace;

# Child of the zygote.
allow system_server zygote:fd use;
allow system_server zygote:process sigchld;

# May kill zygote on crashes.
allow system_server zygote:process sigkill;
allow system_server crash_dump:process sigkill;

# Read /system/bin/app_process.
allow system_server zygote_exec:file r_file_perms;

# Needed to close the zygote socket, which involves getopt / getattr
allow system_server zygote:unix_stream_socket { getopt getattr };

# system server gets network and bluetooth permissions.
net_domain(system_server)
# in addition to ioctls whitelisted for all domains, also allow system_server
# to use privileged ioctls commands. Needed to set up VPNs.
allowxperm system_server self:udp_socket ioctl priv_sock_ioctls;
bluetooth_domain(system_server)

# These are the capabilities assigned by the zygote to the
# system server.
allow system_server self:capability {
    ipc_lock
    kill
    net_admin
    net_bind_service
    net_broadcast
    net_raw
    sys_boot
    sys_nice
    sys_resource
    sys_time
    sys_tty_config
};

wakelock_use(system_server)

# Triggered by /proc/pid accesses, not allowed.
dontaudit system_server self:capability sys_ptrace;

# Trigger module auto-load.
allow system_server kernel:system module_request;

# Allow alarmtimers to be set
allow system_server self:capability2 wake_alarm;

# Use netlink uevent sockets.
allow system_server self:netlink_kobject_uevent_socket create_socket_perms_no_ioctl;

# Use generic netlink sockets.
allow system_server self:netlink_socket create_socket_perms_no_ioctl;
allow system_server self:netlink_generic_socket create_socket_perms_no_ioctl;

# Use generic "sockets" where the address family is not known
# to the kernel. The ioctl permission is specifically omitted here, but may
# be added to device specific policy along with the ioctl commands to be
# whitelisted.
allow system_server self:socket create_socket_perms_no_ioctl;

# Set and get routes directly via netlink.
allow system_server self:netlink_route_socket nlmsg_write;

# Kill apps.
allow system_server appdomain:process { sigkill signal };

# Set scheduling info for apps.
allow system_server appdomain:process { getsched setsched };
allow system_server audioserver:process { getsched setsched };
allow system_server hal_audio:process { getsched setsched };
allow system_server cameraserver:process { getsched setsched };
allow system_server mediaserver:process { getsched setsched };
allow system_server bootanim:process { getsched setsched };

# Read /proc/pid data for all domains. This is used by ProcessCpuTracker
# within system_server to keep track of memory and CPU usage for
# all processes on the device. In addition, /proc/pid files access is needed
# for dumping stack traces of native processes.
r_dir_file(system_server, domain)

# Read/Write to /proc/net/xt_qtaguid/ctrl and and /dev/xt_qtaguid.
allow system_server qtaguid_proc:file rw_file_perms;
allow system_server qtaguid_device:chr_file rw_file_perms;

# Read /proc/uid_cputime/show_uid_stat.
allow system_server proc_uid_cputime_showstat:file r_file_perms;

# Write /proc/uid_cputime/remove_uid_range.
allow system_server proc_uid_cputime_removeuid:file { w_file_perms getattr };

# Write /proc/uid_procstat/set.
allow system_server proc_uid_procstat_set:file { w_file_perms getattr };

# Write to /proc/sysrq-trigger.
allow system_server proc_sysrq:file rw_file_perms;

# Read /proc/stat for CPU usage statistics
allow system_server proc_stat:file r_file_perms;

# Read /sys/kernel/debug/wakeup_sources.
allow system_server debugfs:file r_file_perms;

# The DhcpClient and WifiWatchdog use packet_sockets
allow system_server self:packet_socket create_socket_perms_no_ioctl;

# NetworkDiagnostics requires explicit bind() calls to ping sockets. These aren't actually the same
# as raw sockets, but the kernel doesn't yet distinguish between the two.
allow system_server node:rawip_socket node_bind;

# 3rd party VPN clients require a tun_socket to be created
allow system_server self:tun_socket create_socket_perms_no_ioctl;

# Talk to init and various daemons via sockets.
unix_socket_connect(system_server, lmkd, lmkd)
unix_socket_connect(system_server, mtpd, mtp)
unix_socket_connect(system_server, netd, netd)
unix_socket_connect(system_server, vold, vold)
unix_socket_connect(system_server, webview_zygote, webview_zygote)
unix_socket_connect(system_server, zygote, zygote)
unix_socket_connect(system_server, racoon, racoon)
unix_socket_send(system_server, wpa, wpa)
unix_socket_connect(system_server, uncrypt, uncrypt)

# Communicate over a socket created by surfaceflinger.
allow system_server surfaceflinger:unix_stream_socket { read write setopt };

# Perform Binder IPC.
binder_use(system_server)
binder_call(system_server, appdomain)
binder_call(system_server, binderservicedomain)
binder_call(system_server, dumpstate)
binder_call(system_server, fingerprintd)
binder_call(system_server, hal_fingerprint)
binder_call(system_server, gatekeeperd)
binder_call(system_server, installd)
binder_call(system_server, netd)
binder_call(system_server, wificond)
binder_service(system_server)

# Perform HwBinder IPC.
hwbinder_use(system_server)
binder_call(system_server, hal_bluetooth)
binder_call(system_server, hal_boot)
binder_call(system_server, hal_contexthub)
binder_call(system_server, hal_fingerprint)
binder_call(system_server, hal_gnss);
binder_call(system_server, hal_fingerprint)
binder_call(system_server, hal_ir)
binder_call(system_server, hal_light)
binder_call(system_server, hal_memtrack)
binder_call(system_server, hal_power)
binder_call(system_server, hal_sensors)
binder_call(system_server, hal_thermal)
binder_call(system_server, hal_vibrator)
binder_call(system_server, hal_vr)
binder_call(system_server, hal_wifi)
binder_call(system_server, wpa)

# Talk to tombstoned to get ANR traces.
unix_socket_connect(system_server, tombstoned_intercept, tombstoned)

# Send signals to trigger ANR traces.
# This is derived from the list that system server defines as interesting native processes
# to dump during ANRs or watchdog aborts, defined in NATIVE_STACKS_OF_INTEREST in
# frameworks/base/services/core/java/com/android/server/Watchdog.java.
allow system_server {
  audioserver
  cameraserver
  drmserver
  inputflinger
  mediacodec
  mediadrmserver
  mediaextractor
  mediaserver
  mediaanalytics
  sdcardd
  surfaceflinger
}:process { signal };

# Use sockets received over binder from various services.
allow system_server audioserver:tcp_socket rw_socket_perms;
allow system_server audioserver:udp_socket rw_socket_perms;
allow system_server mediaserver:tcp_socket rw_socket_perms;
allow system_server mediaserver:udp_socket rw_socket_perms;

# Use sockets received over binder from various services.
allow system_server mediadrmserver:tcp_socket rw_socket_perms;
allow system_server mediadrmserver:udp_socket rw_socket_perms;

# Check SELinux permissions.
selinux_check_access(system_server)

# XXX Label sysfs files with a specific type?
allow system_server sysfs:file rw_file_perms;
allow system_server sysfs_nfc_power_writable:file rw_file_perms;
allow system_server sysfs_devices_system_cpu:file w_file_perms;
allow system_server sysfs_mac_address:file r_file_perms;
allow system_server sysfs_thermal:dir search;
allow system_server sysfs_thermal:file r_file_perms;

# TODO: Remove when HALs are forced into separate processes
allow system_server sysfs_vibrator:file { write append };

# TODO: added to match above sysfs rule. Remove me?
allow system_server sysfs_usb:file w_file_perms;

# Access devices.
allow system_server device:dir r_dir_perms;
allow system_server mdns_socket:sock_file rw_file_perms;
allow system_server alarm_device:chr_file rw_file_perms;
allow system_server gpu_device:chr_file rw_file_perms;
allow system_server iio_device:chr_file rw_file_perms;
allow system_server input_device:dir r_dir_perms;
allow system_server input_device:chr_file rw_file_perms;
allow system_server radio_device:chr_file r_file_perms;
allow system_server tty_device:chr_file rw_file_perms;
allow system_server usbaccessory_device:chr_file rw_file_perms;
allow system_server video_device:dir r_dir_perms;
allow system_server video_device:chr_file rw_file_perms;
allow system_server adbd_socket:sock_file rw_file_perms;
allow system_server rtc_device:chr_file rw_file_perms;
allow system_server audio_device:dir r_dir_perms;

# write access needed for MIDI
allow system_server audio_device:chr_file rw_file_perms;

# tun device used for 3rd party vpn apps
allow system_server tun_device:chr_file rw_file_perms;

# Manage system data files.
allow system_server system_data_file:dir create_dir_perms;
allow system_server system_data_file:notdevfile_class_set create_file_perms;
allow system_server keychain_data_file:dir create_dir_perms;
allow system_server keychain_data_file:file create_file_perms;
allow system_server keychain_data_file:lnk_file create_file_perms;

# Manage /data/app.
allow system_server apk_data_file:dir create_dir_perms;
allow system_server apk_data_file:{ file lnk_file } { create_file_perms link };
allow system_server apk_tmp_file:dir create_dir_perms;
allow system_server apk_tmp_file:file create_file_perms;

# Manage /data/app-private.
allow system_server apk_private_data_file:dir create_dir_perms;
allow system_server apk_private_data_file:file create_file_perms;
allow system_server apk_private_tmp_file:dir create_dir_perms;
allow system_server apk_private_tmp_file:file create_file_perms;

# Manage /data/app-ephemeral
allow system_server ephemeral_apk_data_file:dir create_dir_perms;
allow system_server ephemeral_apk_data_file:file create_file_perms;
allow system_server ephemeral_apk_tmp_file:dir create_dir_perms;
allow system_server ephemeral_apk_tmp_file:file create_file_perms;

# Manage files within asec containers.
allow system_server asec_apk_file:dir create_dir_perms;
allow system_server asec_apk_file:file create_file_perms;
allow system_server asec_public_file:file create_file_perms;

# Manage /data/anr.
allow system_server anr_data_file:dir create_dir_perms;
allow system_server anr_data_file:file create_file_perms;

# Manage /data/backup.
allow system_server backup_data_file:dir create_dir_perms;
allow system_server backup_data_file:file create_file_perms;

# Write to /data/system/heapdump
allow system_server heapdump_data_file:dir rw_dir_perms;
allow system_server heapdump_data_file:file create_file_perms;

# Manage /data/misc/adb.
allow system_server adb_keys_file:dir create_dir_perms;
allow system_server adb_keys_file:file create_file_perms;

# Manage /data/misc/sms.
# TODO:  Split into a separate type?
allow system_server radio_data_file:dir create_dir_perms;
allow system_server radio_data_file:file create_file_perms;

# Manage /data/misc/systemkeys.
allow system_server systemkeys_data_file:dir create_dir_perms;
allow system_server systemkeys_data_file:file create_file_perms;

# Access /data/tombstones.
allow system_server tombstone_data_file:dir r_dir_perms;
allow system_server tombstone_data_file:file r_file_perms;

# Manage /data/misc/vpn.
allow system_server vpn_data_file:dir create_dir_perms;
allow system_server vpn_data_file:file create_file_perms;

# Manage /data/misc/wifi.
allow system_server wifi_data_file:dir create_dir_perms;
allow system_server wifi_data_file:file create_file_perms;

# Manage /data/misc/zoneinfo.
allow system_server zoneinfo_data_file:dir create_dir_perms;
allow system_server zoneinfo_data_file:file create_file_perms;

# Walk /data/data subdirectories.
# Types extracted from seapp_contexts type= fields.
allow system_server { system_app_data_file bluetooth_data_file nfc_data_file radio_data_file shell_data_file app_data_file ephemeral_data_file }:dir { getattr read search };
# Also permit for unlabeled /data/data subdirectories and
# for unlabeled asec containers on upgrades from 4.2.
allow system_server unlabeled:dir r_dir_perms;
# Read pkg.apk file before it has been relabeled by vold.
allow system_server unlabeled:file r_file_perms;

# Populate com.android.providers.settings/databases/settings.db.
allow system_server system_app_data_file:dir create_dir_perms;
allow system_server system_app_data_file:file create_file_perms;

# Receive and use open app data files passed over binder IPC.
# Types extracted from seapp_contexts type= fields.
allow system_server { system_app_data_file bluetooth_data_file nfc_data_file radio_data_file shell_data_file app_data_file }:file { getattr read write append };

# Access to /data/media for measuring disk usage.
allow system_server media_rw_data_file:dir { search getattr open read };

# Receive and use open /data/media files passed over binder IPC.
# Also used for measuring disk usage.
allow system_server media_rw_data_file:file { getattr read write append };

# Relabel apk files.
allow system_server { apk_tmp_file apk_private_tmp_file ephemeral_apk_tmp_file }:{ dir file } { relabelfrom relabelto };
allow system_server { apk_data_file apk_private_data_file ephemeral_apk_data_file}:{ dir file } { relabelfrom relabelto };

# Relabel wallpaper.
allow system_server system_data_file:file relabelfrom;
allow system_server wallpaper_file:file relabelto;
allow system_server wallpaper_file:file { rw_file_perms rename unlink };

# Backup of wallpaper imagery uses temporary hard links to avoid data churn
allow system_server { system_data_file wallpaper_file }:file link;

# ShortcutManager icons
allow system_server system_data_file:dir relabelfrom;
allow system_server shortcut_manager_icons:dir { create_dir_perms relabelto };
allow system_server shortcut_manager_icons:file create_file_perms;

# Manage ringtones.
allow system_server ringtone_file:dir { create_dir_perms relabelto };
allow system_server ringtone_file:file create_file_perms;

# Relabel icon file.
allow system_server icon_file:file relabelto;
allow system_server icon_file:file { rw_file_perms unlink };

# FingerprintService.java does a restorecon of the directory /data/system/users/[0-9]+/fpdata(/.*)?
allow system_server system_data_file:dir relabelfrom;

# Property Service write
set_prop(system_server, system_prop)
set_prop(system_server, safemode_prop)
set_prop(system_server, dhcp_prop)
set_prop(system_server, net_radio_prop)
set_prop(system_server, system_radio_prop)
set_prop(system_server, debug_prop)
set_prop(system_server, powerctl_prop)
set_prop(system_server, fingerprint_prop)
set_prop(system_server, device_logging_prop)
set_prop(system_server, wifi_prop)
set_prop(system_server, dumpstate_options_prop)
set_prop(system_server, overlay_prop)
userdebug_or_eng(`set_prop(system_server, wifi_log_prop)')

# ctl interface
set_prop(system_server, ctl_default_prop)
set_prop(system_server, ctl_bugreport_prop)

# cppreopt property
set_prop(system_server, cppreopt_prop)

# Collect metrics on boot time created by init
get_prop(system_server, boottime_prop)

# Read device's serial number from system properties
get_prop(system_server, serialno_prop)

# Read/write the property which keeps track of whether this is the first start of system_server
set_prop(system_server, firstboot_prop)

# Create a socket for receiving info from wpa.
allow system_server wpa_socket:dir rw_dir_perms;
allow system_server system_wpa_socket:sock_file create_file_perms;

# Remove sockets created by wpa_supplicant
allow system_server wpa_socket:sock_file unlink;

# Create a socket for connections from debuggerd.
allow system_server system_ndebug_socket:sock_file create_file_perms;

# Manage cache files.
allow system_server { cache_file cache_recovery_file }:dir { relabelfrom create_dir_perms };
allow system_server { cache_file cache_recovery_file }:file { relabelfrom create_file_perms };
allow system_server { cache_file cache_recovery_file }:fifo_file create_file_perms;

allow system_server system_file:dir r_dir_perms;
allow system_server system_file:lnk_file r_file_perms;

# LocationManager(e.g, GPS) needs to read and write
# to uart driver and ctrl proc entry
allow system_server gps_control:file rw_file_perms;

# Allow system_server to use app-created sockets and pipes.
allow system_server appdomain:{ tcp_socket udp_socket } { getattr getopt setopt read write shutdown };
allow system_server appdomain:{ fifo_file unix_stream_socket } { getattr read write };

# Allow abstract socket connection
allow system_server rild:unix_stream_socket connectto;

# BackupManagerService needs to manipulate backup data files
allow system_server cache_backup_file:dir rw_dir_perms;
allow system_server cache_backup_file:file create_file_perms;
# LocalTransport works inside /cache/backup
allow system_server cache_private_backup_file:dir create_dir_perms;
allow system_server cache_private_backup_file:file create_file_perms;

# Allow system to talk to usb device
allow system_server usb_device:chr_file rw_file_perms;
allow system_server usb_device:dir r_dir_perms;

# Allow system to talk to sensors
allow system_server sensors_device:chr_file rw_file_perms;

# Read from HW RNG (needed by EntropyMixer).
allow system_server hw_random_device:chr_file r_file_perms;

# Read and delete files under /dev/fscklogs.
r_dir_file(system_server, fscklogs)
allow system_server fscklogs:dir { write remove_name };
allow system_server fscklogs:file unlink;

# logd access, system_server inherit logd write socket
# (urge is to deprecate this long term)
allow system_server zygote:unix_dgram_socket write;

# Read from log daemon.
read_logd(system_server)

# Be consistent with DAC permissions. Allow system_server to write to
# /sys/module/lowmemorykiller/parameters/adj
# /sys/module/lowmemorykiller/parameters/minfree
allow system_server sysfs_lowmemorykiller:file { getattr w_file_perms };

# Read /sys/fs/pstore/console-ramoops
# Don't worry about overly broad permissions for now, as there's
# only one file in /sys/fs/pstore
allow system_server pstorefs:dir r_dir_perms;
allow system_server pstorefs:file r_file_perms;

# /sys access
allow system_server sysfs_zram:dir search;
allow system_server sysfs_zram:file r_file_perms;

allow system_server audioserver_service:service_manager find;
allow system_server batteryproperties_service:service_manager find;
allow system_server cameraserver_service:service_manager find;
allow system_server drmserver_service:service_manager find;
allow system_server dumpstate_service:service_manager find;
allow system_server fingerprintd_service:service_manager find;
allow system_server hal_fingerprint_service:service_manager find;
allow system_server gatekeeper_service:service_manager find;
allow system_server installd_service:service_manager find;
allow system_server keystore_service:service_manager find;
allow system_server mediaserver_service:service_manager find;
allow system_server mediaanalytics_service:service_manager find;
allow system_server mediaextractor_service:service_manager find;
allow system_server mediacodec_service:service_manager find;
allow system_server mediadrmserver_service:service_manager find;
allow system_server netd_service:service_manager find;
allow system_server nfc_service:service_manager find;
allow system_server radio_service:service_manager find;
allow system_server system_server_service:service_manager { add find };
allow system_server surfaceflinger_service:service_manager find;
allow system_server wificond_service:service_manager find;

allow system_server keystore:keystore_key {
	get_state
	get
	insert
	delete
	exist
	list
	reset
	password
	lock
	unlock
	is_empty
	sign
	verify
	grant
	duplicate
	clear_uid
	add_auth
	user_changed
};

# Allow system server to search and write to the persistent factory reset
# protection partition. This block device does not get wiped in a factory reset.
allow system_server block_device:dir search;
allow system_server frp_block_device:blk_file rw_file_perms;

# Clean up old cgroups
allow system_server cgroup:dir { remove_name rmdir };

# /oem access
r_dir_file(system_server, oemfs)

# Allow resolving per-user storage symlinks
allow system_server { mnt_user_file storage_file }:dir { getattr search };
allow system_server { mnt_user_file storage_file }:lnk_file { getattr read };

# Allow statfs() on storage devices, which happens fast enough that
# we shouldn't be killed during unsafe removal
allow system_server sdcard_type:dir { getattr search };

# Traverse into expanded storage
allow system_server mnt_expand_file:dir r_dir_perms;

# Allow system process to relabel the fingerprint directory after mkdir
# and delete the directory and files when no longer needed
allow system_server fingerprintd_data_file:dir { r_dir_perms remove_name rmdir relabelto write };
allow system_server fingerprintd_data_file:file { getattr unlink };

# Allow system process to read network MAC address
allow system_server sysfs_mac_address:file r_file_perms;

userdebug_or_eng(`
  # Allow system server to create and write method traces in /data/misc/trace.
  allow system_server method_trace_data_file:dir w_dir_perms;
  allow system_server method_trace_data_file:file { create w_file_perms };

  # Allow system server to read dmesg
  allow system_server kernel:system syslog_read;
')

# For AppFuse.
allow system_server vold:fd use;
allow system_server fuse_device:chr_file { read write ioctl getattr };
allow system_server app_fuse_file:dir rw_dir_perms;
allow system_server app_fuse_file:file { read write open getattr append };

# For configuring sdcardfs
allow system_server configfs:dir { create_dir_perms };
allow system_server configfs:file { getattr open unlink write };

# Connect to adbd and use a socket transferred from it.
# Used for e.g. jdwp.
allow system_server adbd:unix_stream_socket connectto;
allow system_server adbd:fd use;
allow system_server adbd:unix_stream_socket { getattr getopt ioctl read write shutdown };

# Allow invoking tools like "timeout"
allow system_server toolbox_exec:file rx_file_perms;

# Postinstall
#
# For OTA dexopt, allow calls coming from postinstall.
binder_call(system_server, postinstall)

allow system_server postinstall:fifo_file write;
allow system_server update_engine:fd use;
allow system_server update_engine:fifo_file write;

# Access to /data/preloads
allow system_server preloads_data_file:file { r_file_perms unlink };
allow system_server preloads_data_file:dir { r_dir_perms write remove_name rmdir };

r_dir_file(system_server, cgroup)
allow system_server ion_device:chr_file r_file_perms;
allow system_server hal_graphics_allocator:fd use;

r_dir_file(system_server, proc)
r_dir_file(system_server, proc_meminfo)
r_dir_file(system_server, proc_net)
r_dir_file(system_server, rootfs)
r_dir_file(system_server, sysfs_type)

# Allow system_server to make binder calls to hwservicemanager
binder_call(system_server, hwservicemanager)

userdebug_or_eng(`
  # Allow WifiService to start, stop, and read wifi-specific trace events.
  allow system_server debugfs_tracing_instances:dir search;
  allow system_server debugfs_wifi_tracing:file rw_file_perms;
')

###
### Neverallow rules
###
### system_server should NEVER do any of this

# Do not allow opening files from external storage as unsafe ejection
# could cause the kernel to kill the system_server.
neverallow system_server sdcard_type:dir { open read write };
neverallow system_server sdcard_type:file rw_file_perms;

# system server should never be operating on zygote spawned app data
# files directly. Rather, they should always be passed via a
# file descriptor.
# Types extracted from seapp_contexts type= fields, excluding
# those types that system_server needs to open directly.
neverallow system_server { bluetooth_data_file nfc_data_file shell_data_file app_data_file }:file { open create unlink link };

# Forking and execing is inherently dangerous and racy. See, for
# example, https://www.linuxprogrammingblog.com/threads-and-fork-think-twice-before-using-them
# Prevent the addition of new file execs to stop the problem from
# getting worse. b/28035297
neverallow system_server { file_type -toolbox_exec -logcat_exec }:file execute_no_trans;

# Ensure that system_server doesn't perform any domain transitions other than
# transitioning to the crash_dump domain when a crash occurs.
neverallow system_server { domain -crash_dump }:process transition;
neverallow system_server *:process dyntransition;

# Only allow crash_dump to connect to system_ndebug_socket.
neverallow { domain -init -system_server -crash_dump } system_ndebug_socket:sock_file { open write };

# system_server should never be executing dex2oat. This is either
# a bug (for example, bug 16317188), or represents an attempt by
# system server to dynamically load a dex file, something we do not
# want to allow.
neverallow system_server dex2oat_exec:file no_x_file_perms;

# system_server should never execute or load executable shared libraries
# in /data except for /data/dalvik-cache files.
neverallow system_server {
  data_file_type
  -dalvikcache_data_file #mapping with PROT_EXEC
}:file no_x_file_perms;

# The only block device system_server should be accessing is
# the frp_block_device. This helps avoid a system_server to root
# escalation by writing to raw block devices.
neverallow system_server { dev_type -frp_block_device }:blk_file no_rw_file_perms;

# system_server should never use JIT functionality
neverallow system_server self:process execmem;
neverallow system_server ashmem_device:chr_file execute;