libblkid: udf: Fix parsing LVID location

And add comment about Logical Volume Integrity Sequence that we do not scan it fully.

diff --git a/libblkid/src/superblocks/udf.c b/libblkid/src/superblocks/udf.c
index ee5b26990f6a5300ce0225afc7bd2f5eff1c5337..a6af43e13b53666de7f169c1ea55eb7d3ce51717 100644 (file)
--- a/libblkid/src/superblocks/udf.c
+++ b/libblkid/src/superblocks/udf.c
@@ -350,8 +350,12 @@ real_blksz:
                        }
                } else if (type == TAG_ID_LVD) {
                        if (!lvid_count || !lvid_loc) {
-                               lvid_count = le32_to_cpu(vd->type.logical.lvid_length) / bs;
-                               lvid_loc = le32_to_cpu(vd->type.logical.lvid_location);
+                               uint32_t num_partition_maps = le32_to_cpu(vd->type.logical.num_partition_maps);
+                               /* ECMA-167 3/10.6.12: If num_partition_maps is 0, then no LVID is specified */
+                               if (num_partition_maps) {
+                                       lvid_count = le32_to_cpu(vd->type.logical.lvid_length) / bs;
+                                       lvid_loc = le32_to_cpu(vd->type.logical.lvid_location);
+                               }
                        }
                        if (!have_logvolid || !have_label) {
                                /* LogicalVolumeIdentifier in UDF 2.01 specification:
@@ -415,6 +419,11 @@ real_blksz:
                        if (le32_to_cpu(vd->tag.location) != lvid_loc + b)
                                break;
                        if (type == TAG_ID_LVID && UDF_LVIDIU_LENGTH(*vd) >= sizeof(*lvidiu)) {
+                               /* ECMA-167 3/8.8.2: There is stored sequence of LVIDs and valid is just last
+                                * one. So correctly we should jump to next_lvid_location and read next LVID
+                                * until we find last one. This could be time consuming process and could
+                                * lead to scanning lot of disk blocks. Because we use LVID only for UDF
+                                * version, in the worst case we would report only wrong ID_FS_VERSION. */
                                uint16_t udf_rev;
                                lvidiu = (struct logical_vol_integ_descriptor_imp_use *)
                                        blkid_probe_get_buffer(pr,