--- zzzz-none-000/linux-3.10.107/arch/blackfin/kernel/ptrace.c	2017-06-27 09:49:32.000000000 +0000
+++ scorpion-7490-727/linux-3.10.107/arch/blackfin/kernel/ptrace.c	2021-02-04 17:41:59.000000000 +0000
@@ -117,6 +117,7 @@
 int
 is_user_addr_valid(struct task_struct *child, unsigned long start, unsigned long len)
 {
+	bool valid;
 	struct vm_area_struct *vma;
 	struct sram_list_struct *sraml;
 
@@ -124,9 +125,12 @@
 	if (start + len < start)
 		return -EIO;
 
+	down_read(&child->mm->mmap_sem);
 	vma = find_vma(child->mm, start);
-	if (vma && start >= vma->vm_start && start + len <= vma->vm_end)
-			return 0;
+	valid = vma && start >= vma->vm_start && start + len <= vma->vm_end;
+	up_read(&child->mm->mmap_sem);
+	if (valid)
+		return 0;
 
 	for (sraml = child->mm->context.sram_list; sraml; sraml = sraml->next)
 		if (start >= (unsigned long)sraml->addr