efi_loader: Trigger capsule updates with automatically generated boot options

The EFI spec in §8.5.5 says
"The directory \EFI\UpdateCapsule is checked for capsules only within
 the EFI system partition on the device specified in the active boot
 option determine by reference to BootNext variable or BootOrder variable
 processing."

Automatically generated boot options don't point to the ESP, they point to
the disk itself and find_handle() won't match when searching for an ESP
during a capsule update.
This happens because find_handle() only matches device paths that are
shorter or equal to the device path passed as an argument.
Since the EFI spec allows it we want to allow capsule updates, when the
boot option points to a disk, but that disk contains an ESP with a
\EFI\UpdateCapsule directory.

So, let's change device_is_present_and_system_part() and check if the
supplied device path contains an ESP. If it does return the handle of
the device. Otherwise, iterate over child devices and return the handle
of the first child that contains an ESP.

The returned handle can then be reused later. Rather than calling
efi_fs_from_path(), we can simply look up the EFI_SIMPLE_FILE_SYSTEM_PROTOCOL
on the discovered handle, avoiding the need to re-parse device paths.

Reported-by: Balaji Selvanathan <[email protected]>
Reported-by: John Toomey <[email protected]>
Signed-off-by: Ilias Apalodimas <[email protected]>
Reviewed-by: Heinrich Schuchardt <[email protected]>

0 files changed, 0 insertions, 0 deletions