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 proc_cmdline:file r_file_perms;
dontaudit vendor_misc_writer sysfs_dt_firmware_android:dir search;
dontaudit vendor_misc_writer proc_bootconfig:file r_file_perms;

# Allow ReadDefaultFstab().
read_fstab(vendor_misc_writer)
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 proc_cmdline:file r_file_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			`dontaudit vendor_misc_writer sysfs_dt_firmware_android:dir search;`
Suppress error log coming from libfstab operation vendor_misc_writer includes libfstab, which will carry out libfstab operations without really needing it to do misc writing. Therefore I suppress the error here. Bug: 181277852 Test: boot with no relevant log showing up Change-Id: Ibadb797799606ec8eba4b4e7b35885bb11cb1ff0 2021-02-26 04:17:29 +01:00			`dontaudit vendor_misc_writer proc_bootconfig:file r_file_perms;`
Add rules for calling ReadDefaultFstab() Grant ReadDefaultFstab() callers allow scontext { metadata_file gsi_metadata_file_type }:dir search; allow scontext gsi_public_metadata_file:file r_file_perms; so they can search / read DSU metadata files. The DSU metadata files are required to deduce the correct fstab. Also tighten the neverallow rules in gsid.te. Bug: 181110285 Test: Build pass, presubmit test Test: Boot and check avc denials Test: Boot with DSU and check avc denials Change-Id: Ie464b9a8f7a89f9cf8f4e217dad1322ba3ad0633 2021-03-22 06:46:12 +01:00
			`# Allow ReadDefaultFstab().`
			`read_fstab(vendor_misc_writer)`