platform_system_sepolicy/public/fsck.te

# Any fsck program run by init
type fsck, domain, domain_deprecated;
type fsck_exec, exec_type, file_type;

# /dev/__null__ created by init prior to policy load,
# open fd inherited by fsck.
allow fsck tmpfs:chr_file { read write ioctl };

# Inherit and use pty created by android_fork_execvp_ext().
allow fsck devpts:chr_file { read write ioctl getattr };

# Allow stdin/out back to vold
allow fsck vold:fd use;
allow fsck vold:fifo_file { read write getattr };

# Run fsck on certain block devices
allow fsck block_device:dir search;
allow fsck userdata_block_device:blk_file rw_file_perms;
allow fsck cache_block_device:blk_file rw_file_perms;
allow fsck dm_device:blk_file rw_file_perms;

# fsck performs a stat() on swap to verify that it is a valid
# swap device before setting the EXT2_MF_SWAP mount flag.
allow fsck swap_block_device:blk_file getattr;

r_dir_file(fsck, proc)

###
### neverallow rules
###

# fsck should never be run on these block devices
neverallow fsck {
  boot_block_device
  frp_block_device
  metadata_block_device
  recovery_block_device
  root_block_device
  swap_block_device
  system_block_device
  vold_device
}:blk_file no_rw_file_perms;

# Only allow entry from init or vold via fsck binaries
neverallow { domain -init -vold } fsck:process transition;
neverallow * fsck:process dyntransition;
neverallow fsck { file_type fs_type -fsck_exec }:file entrypoint;