android10/system/sepolicy/public/lmkd.te

# lmkd low memory killer daemon
type lmkd, domain, mlstrustedsubject;
type lmkd_exec, system_file_type, exec_type, file_type;

allow lmkd self:global_capability_class_set { dac_override dac_read_search sys_resource kill };

# lmkd locks itself in memory, to prevent it from being
# swapped out and unable to kill other memory hogs.
# system/core commit b28ff9131363f7b4a698990da5748b2a88c3ed35
# b/16236289
allow lmkd self:global_capability_class_set ipc_lock;

## Open and write to /proc/PID/oom_score_adj
## TODO: maybe scope this down?
r_dir_file(lmkd, appdomain)
allow lmkd appdomain:file write;
r_dir_file(lmkd, system_server)
allow lmkd system_server:file write;

## Writes to /sys/module/lowmemorykiller/parameters/minfree
r_dir_file(lmkd, sysfs_lowmemorykiller)
allow lmkd sysfs_lowmemorykiller:file w_file_perms;

# setsched and send kill signals
allow lmkd appdomain:process { setsched sigkill };
allow lmkd kernel:process { setsched };

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

# Allow to read memcg stats
allow lmkd cgroup:file r_file_perms;

# Set self to SCHED_FIFO
allow lmkd self:global_capability_class_set sys_nice;

allow lmkd proc_zoneinfo:file r_file_perms;

# Set sys.lmk.* properties.
set_prop(lmkd, system_lmk_prop)

# live lock watchdog process allowed to look through /proc/
allow lmkd domain:dir { search open read };
allow lmkd domain:file { open read };

# live lock watchdog process allowed to dump process trace and
# reboot because orderly shutdown may not be possible.
allow lmkd proc_sysrq:file rw_file_perms;

# Read /proc/meminfo
allow lmkd proc_meminfo:file r_file_perms;

# Read /proc/pressure/cpu and /proc/pressure/io
allow lmkd proc_pressure_cpu:file r_file_perms;
allow lmkd proc_pressure_io:file r_file_perms;

# Read/Write /proc/pressure/memory
allow lmkd proc_pressure_mem:file rw_file_perms;

# Allow lmkd to write to statsd.
unix_socket_send(lmkd, statsdw, statsd)

### neverallow rules

# never honor LD_PRELOAD
neverallow * lmkd:process noatsecure;