1 files changed, 42 insertions, 5 deletions

diff --git a/mm/util.c b/mm/util.c
index 5f4bb59da63c..7368479220b3 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -1,20 +1,22 @@
 #include <linux/slab.h>
 #include <linux/string.h>
 #include <linux/module.h>
+#include <linux/err.h>
+#include <asm/uaccess.h>
 
 /**
- * kzalloc - allocate memory. The memory is set to zero.
+ * __kzalloc - allocate memory. The memory is set to zero.
  * @size: how many bytes of memory are required.
  * @flags: the type of memory to allocate.
  */
-void *kzalloc(size_t size, gfp_t flags)
+void *__kzalloc(size_t size, gfp_t flags)
 {
-        void *ret = kmalloc(size, flags);
+        void *ret = ____kmalloc(size, flags);
         if (ret)
                 memset(ret, 0, size);
         return ret;
 }
-EXPORT_SYMBOL(kzalloc);
+EXPORT_SYMBOL(__kzalloc);
 
 /*
  * kstrdup - allocate space for and copy an existing string
@@ -31,9 +33,44 @@ char *kstrdup(const char *s, gfp_t gfp)
                 return NULL;
 
         len = strlen(s) + 1;
-        buf = kmalloc(len, gfp);
+        buf = ____kmalloc(len, gfp);
         if (buf)
                 memcpy(buf, s, len);
         return buf;
 }
 EXPORT_SYMBOL(kstrdup);
+
+/*
+ * strndup_user - duplicate an existing string from user space
+ *
+ * @s: The string to duplicate
+ * @n: Maximum number of bytes to copy, including the trailing NUL.
+ */
+char *strndup_user(const char __user *s, long n)
+{
+        char *p;
+        long length;
+
+        length = strnlen_user(s, n);
+
+        if (!length)
+                return ERR_PTR(-EFAULT);
+
+        if (length > n)
+                return ERR_PTR(-EINVAL);
+
+        p = kmalloc(length, GFP_KERNEL);
+
+        if (!p)
+                return ERR_PTR(-ENOMEM);
+
+        if (copy_from_user(p, s, length)) {
+                kfree(p);
+                return ERR_PTR(-EFAULT);
+        }
+
+        p[length - 1] = '\0';
+
+        return p;
+}
+EXPORT_SYMBOL(strndup_user);