Re: efi: be more paranoid about available space when creating variables

[Lingzhu Xiang <lxiang-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>]

On 03/26/2013 11:56 AM, Matthew Garrett wrote:
> diff --git a/drivers/firmware/efivars.c b/drivers/firmware/efivars.c
> index 7acafb8..731ac7b 100644
> --- a/drivers/firmware/efivars.c
> +++ b/drivers/firmware/efivars.c
> @@ -436,9 +436,12 @@ static efi_status_t
>   check_var_size_locked(struct efivars *efivars, u32 attributes,
>   			unsigned long size)
>   {
> -	u64 storage_size, remaining_size, max_size;
> +	u64 storage_size, remaining_size, max_size, active_available;
> +	struct efivar_entry *entry;
> +	struct efi_variable *var;
>   	efi_status_t status;
>   	const struct efivar_operations *fops = efivars->ops;
> +	unsigned long active_size = 0;
>
>   	if (!efivars->ops->query_variable_info)
>   		return EFI_UNSUPPORTED;
> @@ -449,8 +452,16 @@ check_var_size_locked(struct efivars *efivars, u32 attributes,
>   	if (status != EFI_SUCCESS)
>   		return status;
>
> +	list_for_each_entry(entry, &efivars->list, list) {
> +		var = &entry->var;
> +		get_var_data_locked(efivars, var);

Check the return value here? Like for an empty efivarfs file,
it would return EFI_NOT_FOUND and active_size += 1024.

> +		active_size += var->DataSize;
> +	}
> +
> +	active_available = storage_size - active_size;
> +
>   	if (!storage_size || size > remaining_size || size > max_size ||
> -	    (remaining_size - size) < (storage_size / 2))
> +	    (active_available - size) < (storage_size / 2))
>   		return EFI_OUT_OF_RESOURCES;
>
>   	return status;
>