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

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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;


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