[PATCH v2] efi_loader: Set variable attributes when EFI_BUFFER_TOO_SMALL is returned

[Heinrich Schuchardt]

On 3/16/22 16:13, 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
>
> Signed-off-by: Ilias Apalodimas <ilias.apalodimas at linaro.org>

Reviewed-by: Heinrich Schuchardt <xypron.glpk at gmx.de>

> ---
> Changes since v1:
> - tmp variables  switched to efi_status_t instead of int
> - switched (ret == EFI_SUCCESS || ret == EFI_BUFFER_TOO_SMALL)
>    to (ret != EFI_SUCCESS && ret != EFI_BUFFER_TOO_SMALL) to
>    make the code easier to read
> - Only call get_property_int() if attributes != NULL
>
>   lib/efi_loader/efi_variable_tee.c | 31 ++++++++++++++++++++-----------
>   1 file changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/lib/efi_loader/efi_variable_tee.c b/lib/efi_loader/efi_variable_tee.c
> index 58931c4efd74..dfef18435dfa 100644
> --- a/lib/efi_loader/efi_variable_tee.c
> +++ b/lib/efi_loader/efi_variable_tee.c
> @@ -368,7 +368,7 @@ efi_status_t efi_get_variable_int(const u16 *variable_name,
>   	efi_uintn_t name_size;
>   	efi_uintn_t tmp_dsize;
>   	u8 *comm_buf = NULL;
> -	efi_status_t ret;
> +	efi_status_t ret, tmp;
>
>   	if (!variable_name || !vendor || !data_size) {
>   		ret = EFI_INVALID_PARAMETER;
> @@ -407,23 +407,32 @@ 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) {
> -		/* Update with reported data size for trimmed case */
> -		*data_size = var_acc->data_size;
> -	}
> -	if (ret != EFI_SUCCESS)
> -		goto out;
> -
> -	ret = get_property_int(variable_name, name_size, vendor, &var_property);
> -	if (ret != EFI_SUCCESS)
> +	if (ret != EFI_SUCCESS && ret != EFI_BUFFER_TOO_SMALL)
>   		goto out;
>
> +	/* 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
> +	 */
>   	if (attributes) {
> +		tmp = get_property_int(variable_name, name_size, vendor,
> +				       &var_property);
> +		if (tmp != EFI_SUCCESS) {
> +			ret = tmp;
> +			goto out;
> +		}
>   		*attributes = var_acc->attr;
> -		if (var_property.property & VAR_CHECK_VARIABLE_PROPERTY_READ_ONLY)
> +		if (var_property.property &
> +		    VAR_CHECK_VARIABLE_PROPERTY_READ_ONLY)
>   			*attributes |= EFI_VARIABLE_READ_ONLY;
>   	}
>
> +	/* return if ret is EFI_BUFFER_TOO_SMALL */
> +	if (ret != EFI_SUCCESS)
> +		goto out;
> +
>   	if (data)
>   		memcpy(data, (u8 *)var_acc->name + var_acc->name_size,
>   		       var_acc->data_size);