dm crypt: use kstrdup

Use kstrdup when the goal of an allocation is copy a string into the
allocated region.

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

// <smpl>
@@
expression from,to;
expression flag,E1,E2;
statement S;
@@

-  to = kmalloc(strlen(from) + 1,flag);
+  to = kstrdup(from, flag);
   ... when != \(from = E1 \| to = E1 \)
   if (to==NULL || ...) S
   ... when != \(from = E2 \| to = E2 \)
-  strcpy(to, from);
// </smpl>
Signed-off-by: NJulia Lawall <julia@diku.dk>
Signed-off-by: NAlasdair G Kergon <agk@redhat.com>

drivers/md/dm-crypt.c

@@ -1168,12 +1168,11 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 	if (ivmode && cc->iv_gen_ops) {
 		if (ivopts)
 			*(ivopts - 1) = ':';
-		cc->iv_mode = kmalloc(strlen(ivmode) + 1, GFP_KERNEL);
+		cc->iv_mode = kstrdup(ivmode, GFP_KERNEL);
 		if (!cc->iv_mode) {
 			ti->error = "Error kmallocing iv_mode string";
 			goto bad_ivmode_string;
 		}
-		strcpy(cc->iv_mode, ivmode);
 	} else
 		cc->iv_mode = NULL;