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

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

[Ilias Apalodimas]

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@linaro.org>
---
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);
-- 
2.32.0

Re: [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@linaro.org>

Reviewed-by: Heinrich Schuchardt <xypron.glpk@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);