dm crypt: fix parsing of extended IV arguments

The dm-crypt cipher specification in a mapping table is defined as:
  cipher[:keycount]-chainmode-ivmode[:ivopts]
or (new crypt API format):
  capi:cipher_api_spec-ivmode[:ivopts]

For ESSIV, the parameter includes hash specification, for example:
aes-cbc-essiv:sha256

The implementation expected that additional IV option to never include
another dash '-' character.

But, with SHA3, there are names like sha3-256; so the mapping table
parser fails:

dmsetup create test --table "0 8 crypt aes-cbc-essiv:sha3-256 9c1185a5c5e9fc54612808977ee8f5b9e 0 /dev/sdb 0"
  or (new crypt API format)
dmsetup create test --table "0 8 crypt capi:cbc(aes)-essiv:sha3-256 9c1185a5c5e9fc54612808977ee8f5b9e 0 /dev/sdb 0"

  device-mapper: crypt: Ignoring unexpected additional cipher options
  device-mapper: table: 253:0: crypt: Error creating IV
  device-mapper: ioctl: error adding target to table

Fix the dm-crypt constructor to ignore additional dash in IV options and
also remove a bogus warning (that is ignored anyway).

Cc: stable@vger.kernel.org # 4.12+
Signed-off-by: NMilan Broz <gmazyland@gmail.com>
Signed-off-by: NMike Snitzer <snitzer@redhat.com>

drivers/md/dm-crypt.c

@@ -2414,9 +2414,21 @@ static int crypt_ctr_cipher_new(struct dm_target *ti, char *cipher_in, char *key
 	 * capi:cipher_api_spec-iv:ivopts
 	 */
 	tmp = &cipher_in[strlen("capi:")];
-	cipher_api = strsep(&tmp, "-");
-	*ivmode = strsep(&tmp, ":");
-	*ivopts = tmp;
+
+	/* Separate IV options if present, it can contain another '-' in hash name */
+	*ivopts = strrchr(tmp, ':');
+	if (*ivopts) {
+		**ivopts = '\0';
+		(*ivopts)++;
+	}
+	/* Parse IV mode */
+	*ivmode = strrchr(tmp, '-');
+	if (*ivmode) {
+		**ivmode = '\0';
+		(*ivmode)++;
+	}
+	/* The rest is crypto API spec */
+	cipher_api = tmp;
 
 	if (*ivmode && !strcmp(*ivmode, "lmk"))
 		cc->tfms_count = 64;
@@ -2486,11 +2498,8 @@ static int crypt_ctr_cipher_old(struct dm_target *ti, char *cipher_in, char *key
 		goto bad_mem;
 
 	chainmode = strsep(&tmp, "-");
-	*ivopts = strsep(&tmp, "-");
-	*ivmode = strsep(&*ivopts, ":");
-
-	if (tmp)
-		DMWARN("Ignoring unexpected additional cipher options");
+	*ivmode = strsep(&tmp, ":");
+	*ivopts = tmp;
 
 	/*
 	 * For compatibility with the original dm-crypt mapping format, if