diff --git a/kernel/dma/debug.c b/kernel/dma/debug.c
index 1a5c86d..a6e3792 100644
--- a/kernel/dma/debug.c
+++ b/kernel/dma/debug.c
@@ -62,7 +62,8 @@ enum map_err_types {
  * @pfn: page frame of the start address
  * @offset: offset of mapping relative to pfn
  * @map_err_type: track whether dma_mapping_error() was checked
- * @stacktrace: support backtraces when a violation is detected
+ * @stack_len: number of backtrace entries in @stack_entries
+ * @stack_entries: stack of backtrace history
  */
 struct dma_debug_entry {
 	struct list_head list;
diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 97c298b..b079a9a 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -1136,6 +1136,9 @@ static int swiotlb_find_slots(struct device *dev, phys_addr_t orig_addr,
 	int cpu, i;
 	int index;
 
+	if (alloc_size > IO_TLB_SEGSIZE * IO_TLB_SIZE)
+		return -1;
+
 	cpu = raw_smp_processor_id();
 	for (i = 0; i < default_nareas; ++i) {
 		index = swiotlb_search_area(dev, cpu, i, orig_addr, alloc_size,