1 files changed, 21 insertions, 0 deletions

diff --git a/mm/util.c b/mm/util.c
index 834db7be240f..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