udf: disallow RW mount without valid integrity descriptor

Refuse to mount a volume read-write without a coherent Logical Volume
Integrity Descriptor, because we can't generate truly unique IDs without
one.

This fixes a bug where all inodes created on a UDF filesystem following
mount without a coherent LVID are assigned unique ID 0 which can then
confuse other UDF implementations.

Signed-off-by: Steven J. Magnani <steve@digidescorp.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/super.c

@@ -1474,6 +1474,17 @@ static int udf_load_logicalvol(struct super_block *sb, sector_t block,
 	if (lvd->integritySeqExt.extLength)
 		udf_load_logicalvolint(sb, leea_to_cpu(lvd->integritySeqExt));
 	ret = 0;
+
+	if (!sbi->s_lvid_bh) {
+		/* We can't generate unique IDs without a valid LVID */
+		if (sb_rdonly(sb)) {
+			UDF_SET_FLAG(sb, UDF_FLAG_RW_INCOMPAT);
+		} else {
+			udf_warn(sb, "Damaged or missing LVID, forcing "
+				     "readonly mount\n");
+			ret = -EACCES;
+		}
+	}
 out_bh:
 	brelse(bh);
 	return ret;