platform_system_sepolicy/public/vendor_misc_writer.te

# vendor_misc_writer
type vendor_misc_writer, domain;
type vendor_misc_writer_exec, vendor_file_type, exec_type, file_type;

# Raw writes to misc_block_device
allow vendor_misc_writer misc_block_device:blk_file w_file_perms;
allow vendor_misc_writer block_device:dir r_dir_perms;

# Silence the denial when calling libfstab's ReadDefaultFstab, which tries to
# load DT fstab.
dontaudit vendor_misc_writer gsi_metadata_file:dir search;
dontaudit vendor_misc_writer proc_cmdline:file r_file_perms;
dontaudit vendor_misc_writer metadata_file:dir search;
dontaudit vendor_misc_writer sysfs_dt_firmware_android:dir search;
Add vendor_misc_writer. The space between 2K and 16K in /misc is currently reserved for vendor's use (as claimed in bootloader_message.h), but we don't allow vendor module to access misc_block_device other than vendor_init. The change in the topic adds a `misc_writer` tool as a vendor module, which allows writing data to the vendor space to bridge the gap in the short term. This CL adds matching labels to grant access. Long term goal is to move /misc as vendor owned, then to provide HAL access from core domain (b/132906936). Bug: 132906936 Test: Build crosshatch that includes misc_writer module. Invoke /vendor/bin/misc_writer to write data to /misc. Change-Id: I4c18d78171a839ae5497b3a61800193ef9e51b3b 2019-05-16 23:44:11 +02:00			`# vendor_misc_writer`
			`type vendor_misc_writer, domain;`
			`type vendor_misc_writer_exec, vendor_file_type, exec_type, file_type;`

			`# Raw writes to misc_block_device`
			`allow vendor_misc_writer misc_block_device:blk_file w_file_perms;`
			`allow vendor_misc_writer block_device:dir r_dir_perms;`

Ignore the denial due to vendor_misc_writer reading DT fstab. This CL addresses the following denial, when vendor_misc_writer tries to read DT fstab (i.e. device tree fstab) for /misc entry. avc: denied { search } for comm="misc_writer" name="android" dev="sysfs" ino=17456 scontext=u:r:vendor_misc_writer:s0 tcontext=u:object_r:sysfs_dt_firmware_android:s0 tclass=dir DT fstab was used for devices shipped prior to Q, for early-mounting partitions (e.g. /system, /vendor, /product), which has been disallowed for Q launch devices. vendor_misc_writer is a new module added since Q, so it doesn't need to worry about the legacy code path; in practice there's no benefit of putting /misc entry into DT fstab either. Bug: 134122603 Test: Build and flash taimen with the change that enables vendor_misc_writer. Check that it no longer gives the above denial during boot. Change-Id: Id2fb206706f7cd19a4cde2701e4155bfc03f01b4 2019-06-19 23:30:11 +02:00			`# Silence the denial when calling libfstab's ReadDefaultFstab, which tries to`
			`# load DT fstab.`
Suppress errors that are not needed The purpose of misc_writer is to write misc partition. However, when it includes libfstab, it will probe files like kernal command line (proc/cmdline) and metadata, which are permissions it does not need. Bug: 170189742 Test: Boot under permissive mode and find the errors gone. Change-Id: Icda3200660a3bee5cadb6f5e0026fa71941ae5dc 2020-10-07 10:44:58 +02:00			`dontaudit vendor_misc_writer gsi_metadata_file:dir search;`
			`dontaudit vendor_misc_writer proc_cmdline:file r_file_perms;`
Add vendor_misc_writer. The space between 2K and 16K in /misc is currently reserved for vendor's use (as claimed in bootloader_message.h), but we don't allow vendor module to access misc_block_device other than vendor_init. The change in the topic adds a `misc_writer` tool as a vendor module, which allows writing data to the vendor space to bridge the gap in the short term. This CL adds matching labels to grant access. Long term goal is to move /misc as vendor owned, then to provide HAL access from core domain (b/132906936). Bug: 132906936 Test: Build crosshatch that includes misc_writer module. Invoke /vendor/bin/misc_writer to write data to /misc. Change-Id: I4c18d78171a839ae5497b3a61800193ef9e51b3b 2019-05-16 23:44:11 +02:00			`dontaudit vendor_misc_writer metadata_file:dir search;`
Ignore the denial due to vendor_misc_writer reading DT fstab. This CL addresses the following denial, when vendor_misc_writer tries to read DT fstab (i.e. device tree fstab) for /misc entry. avc: denied { search } for comm="misc_writer" name="android" dev="sysfs" ino=17456 scontext=u:r:vendor_misc_writer:s0 tcontext=u:object_r:sysfs_dt_firmware_android:s0 tclass=dir DT fstab was used for devices shipped prior to Q, for early-mounting partitions (e.g. /system, /vendor, /product), which has been disallowed for Q launch devices. vendor_misc_writer is a new module added since Q, so it doesn't need to worry about the legacy code path; in practice there's no benefit of putting /misc entry into DT fstab either. Bug: 134122603 Test: Build and flash taimen with the change that enables vendor_misc_writer. Check that it no longer gives the above denial during boot. Change-Id: Id2fb206706f7cd19a4cde2701e4155bfc03f01b4 2019-06-19 23:30:11 +02:00			`dontaudit vendor_misc_writer sysfs_dt_firmware_android:dir search;`