drivers/mtd: Use memdup_user

Use memdup_user when user data is immediately copied into the
allocated region.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression from,to,size,flag;
position p;
identifier l1,l2;
@@

-  to = \(kmalloc@p\|kzalloc@p\)(size,flag);
+  to = memdup_user(from,size);
   if (
-      to==NULL
+      IS_ERR(to)
                 || ...) {
   <+... when != goto l1;
-  -ENOMEM
+  PTR_ERR(to)
   ...+>
   }
-  if (copy_from_user(to, from, size) != 0) {
-    <+... when != goto l2;
-    -EFAULT
-    ...+>
-  }
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/mtd/mtdchar.c

@@ -404,14 +404,9 @@ static int mtd_do_writeoob(struct file *file, struct mtd_info *mtd,
 	if (ops.ooboffs && ops.ooblen > (mtd->oobsize - ops.ooboffs))
 		return -EINVAL;
 
-	ops.oobbuf = kmalloc(length, GFP_KERNEL);
-	if (!ops.oobbuf)
-		return -ENOMEM;
-
-	if (copy_from_user(ops.oobbuf, ptr, length)) {
-		kfree(ops.oobbuf);
-		return -EFAULT;
-	}
+	ops.oobbuf = memdup_user(ptr, length);
+	if (IS_ERR(ops.oobbuf))
+		return PTR_ERR(ops.oobbuf);
 
 	start &= ~((uint64_t)mtd->oobsize - 1);
 	ret = mtd->write_oob(mtd, start, &ops);