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
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
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
