diff --git a/arch/blackfin/kernel/ptrace.c b/arch/blackfin/kernel/ptrace.c
index 7e1f762b670052c961e47c31f78f719e96b6c973..140bf00e99749f6fee7e9aec85149f9872c1d03f 100644
--- a/arch/blackfin/kernel/ptrace.c
+++ b/arch/blackfin/kernel/ptrace.c
@@ -160,6 +160,10 @@ static inline int is_user_addr_valid(struct task_struct *child,
 	struct vm_list_struct *vml;
 	struct sram_list_struct *sraml;
 
+	/* overflow */
+	if (start + len < start)
+		return -EIO;
+
 	for (vml = child->mm->context.vmlist; vml; vml = vml->next)
 		if (start >= vml->vma->vm_start && start + len < vml->vma->vm_end)
 			return 0;