[PATCH] efi_loader: Set variable attributes when EFI_BUFFER_TOO_SMALL is returned

[Heinrich Schuchardt]

On 3/16/22 13:55, Ilias Apalodimas wrote:
> Starting UEFI Spec 2.8 we must fill in the variable attributes when
> GetVariable() returns EFI_BUFFER_TOO_SMALL and Attributes is non-NULL.
>
> This code was written with 2.7 in mind so let's move the code around a
> bit and fill in the attributes EFI_BUFFER_TOO_SMALL is returned

In the UEFI spec changelog:

1954 set (*Attributes) when GetVariable() returns EFI_BUFFER_TOO_SMALL
and Attributes is non-NULL

In efi_get_variable_mem() this already works correctly.

>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>
> ---
>   lib/efi_loader/efi_variable_tee.c | 27 ++++++++++++++++++---------
>   1 file changed, 18 insertions(+), 9 deletions(-)
>
> diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
> index 58931c4efd74..33c7dfc53d14 100644
> --- a/lib/efi_loader/efi_variable_tee.c
> +++ b/lib/efi_loader/efi_variable_tee.c
> @@ -408,22 +408,31 @@ efi_status_t efi_get_variable_int(const u16 *variable_name,
>   	/* Communicate */
>   	ret = mm_communicate(comm_buf, payload_size);
>   	if (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL) {

You could make the code easier to read with:

if (ret != EFI_SUCCESS && ret != EFI_BUFFER_TOO_SMALL)
	goto out;

> +		int tmp;
>   		/* Update with reported data size for trimmed case */
>   		*data_size = var_acc->data_size;
> +		/*
> +		 * UEFI > 2.7 needs the attributes set even if the buffer is
> +		 * smaller
> +		 */
> +		tmp = get_property_int(variable_name, name_size, vendor,
> +				       &var_property);

Why call get_property_int() if (!attributes)?
You don't use the data in this case.

Best regards

Heinrich

> +		if (tmp != EFI_SUCCESS) {
> +			ret = tmp;
> +			goto out;
> +		}
> +
> +		if (attributes) {
> +			*attributes = var_acc->attr;
> +			if (var_property.property &
> +			    VAR_CHECK_VARIABLE_PROPERTY_READ_ONLY)
> +				*attributes |= EFI_VARIABLE_READ_ONLY;
> +		}
>   	}
> -	if (ret != EFI_SUCCESS)
> -		goto out;
>
> -	ret = get_property_int(variable_name, name_size, vendor, &var_property);
>   	if (ret != EFI_SUCCESS)
>   		goto out;
>
> -	if (attributes) {
> -		*attributes = var_acc->attr;
> -		if (var_property.property & VAR_CHECK_VARIABLE_PROPERTY_READ_ONLY)
> -			*attributes |= EFI_VARIABLE_READ_ONLY;
> -	}
> -
>   	if (data)
>   		memcpy(data, (u8 *)var_acc->name + var_acc->name_size,
>   		       var_acc->data_size);