1 files changed, 22 insertions, 1 deletions

diff --git a/mm/util.c b/mm/util.c
index 7c35ad95f927..f5712e8964be 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -186,6 +186,27 @@ void kzfree(const void *p)
 }
 EXPORT_SYMBOL(kzfree);
 
+int kern_ptr_validate(const void *ptr, unsigned long size)
+{
+        unsigned long addr = (unsigned long)ptr;
+        unsigned long min_addr = PAGE_OFFSET;
+        unsigned long align_mask = sizeof(void *) - 1;
+
+        if (unlikely(addr < min_addr))
+                goto out;
+        if (unlikely(addr > (unsigned long)high_memory - size))
+                goto out;
+        if (unlikely(addr & align_mask))
+                goto out;
+        if (unlikely(!kern_addr_valid(addr)))
+                goto out;
+        if (unlikely(!kern_addr_valid(addr + size - 1)))
+                goto out;
+        return 1;
+out:
+        return 0;
+}
+
 /*
  * strndup_user - duplicate an existing string from user space
  * @s: The string to duplicate
@@ -220,7 +241,7 @@ char *strndup_user(const char __user *s, long n)
 }
 EXPORT_SYMBOL(strndup_user);
 
-#ifndef HAVE_ARCH_PICK_MMAP_LAYOUT
+#if defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
 void arch_pick_mmap_layout(struct mm_struct *mm)
 {
         mm->mmap_base = TASK_UNMAPPED_BASE;