diff --git a/fs/udf/super.c b/fs/udf/super.c
index 9ac4057..b9306f8 100644
--- a/fs/udf/super.c
+++ b/fs/udf/super.c
@@ -667,6 +667,40 @@ out_unlock:
 	return error;
 }
 
+static int udf_is_vsd_id_valid(loff_t off, const struct volStructDesc* vsd)
+{
+	/* Suppose all valid identifiers are 0-9A-Z */
+	int v = 1;
+	int i;
+	for (i = 0; i < sizeof(vsd->stdIdent); ++i) {
+		int c = vsd->stdIdent[i];
+		/* isalnum(c) gives false positives, eg for 0xff */
+		if ((c < '0' || c > '9') && (c < 'A' || c > 'Z')) {
+			v = 0;
+			break;
+		}
+	}
+#ifdef UDFFS_DEBUG
+	{
+		char hex[sizeof(vsd->stdIdent) * 3 + 1] = { 0 };
+		char chr[sizeof(vsd->stdIdent) + 1 ] = { 0 };
+		char* hp = hex;
+		char* he = hex + sizeof(hex);
+		char* cp = chr;
+		char* ce = chr + sizeof(chr);
+		for (i = 0; i < sizeof(vsd->stdIdent); ++i) {
+			snprintf(hp, he - hp, "%02x ", vsd->stdIdent[i]);
+			hp += 3;
+			snprintf(cp, ce - cp, "%c", vsd->stdIdent[i]);
+			++cp;
+		}
+		pr_notice("%s: at offset 0x%08llx vsd.stdIdent[] = { %s} : %s%s%s%s\n", __func__, off, hex,
+			  v ? "valid" : "invalid", v ? " (" : "", v ? chr : "", v ? ")" : "");
+	}
+#endif
+	return v;
+}
+
 /* Check Volume Structure Descriptors (ECMA 167 2/9.1) */
 /* We also check any "CD-ROM Volume Descriptor Set" (ECMA 167 2/8.3.1) */
 static loff_t udf_check_vsd(struct super_block *sb)
@@ -701,7 +735,7 @@ static loff_t udf_check_vsd(struct super_block *sb)
 		vsd = (struct volStructDesc *)(bh->b_data +
 					      (sector & (sb->s_blocksize - 1)));
 
-		if (vsd->stdIdent[0] == 0) {
+		if (!udf_is_vsd_id_valid(sector, vsd)) {
 			brelse(bh);
 			break;
 		} else if (!strncmp(vsd->stdIdent, VSD_STD_ID_CD001,
@@ -1239,6 +1273,9 @@ static int udf_load_partdesc(struct super_block *sb, sector_t block)
 	 * PHYSICAL partitions are already set up
 	 */
 	type1_idx = i;
+#ifdef UDFFS_DEBUG
+	map = NULL; /* supress 'maybe used uninitialized' warning */
+#endif
 	for (i = 0; i < sbi->s_partitions; i++) {
 		map = &sbi->s_partmaps[i];