udf: Avoid excessive partition lengths

Avoid mounting filesystems where the partition would overflow the
32-bits used for block number. Also refuse to mount filesystems where
the partition length is so large we cannot safely index bits in a
block bitmap.

Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jan Kara <[e-mail]>

fs/udf/super.c

···
 	struct udf_part_map *map;
 	struct udf_sb_info *sbi = UDF_SB(sb);
 	struct partitionHeaderDesc *phd;
+	u32 sum;
 	int err;
 
 	map = &sbi->s_partmaps[p_index];
 
 	map->s_partition_len = le32_to_cpu(p->partitionLength); /* blocks */
 	map->s_partition_root = le32_to_cpu(p->partitionStartingLocation);
+	if (check_add_overflow(map->s_partition_root, map->s_partition_len,
+			       &sum)) {
+		udf_err(sb, "Partition %d has invalid location %u + %u\n",
+			p_index, map->s_partition_root, map->s_partition_len);
+		return -EFSCORRUPTED;
+	}
 
 	if (p->accessType == cpu_to_le32(PD_ACCESS_TYPE_READ_ONLY))
 		map->s_partition_flags |= UDF_PART_FLAG_READ_ONLY;
···
 		bitmap->s_extPosition = le32_to_cpu(
 				phd->unallocSpaceBitmap.extPosition);
 		map->s_partition_flags |= UDF_PART_FLAG_UNALLOC_BITMAP;
+		/* Check whether math over bitmap won't overflow. */
+		if (check_add_overflow(map->s_partition_len,
+				       sizeof(struct spaceBitmapDesc) << 3,
+				       &sum)) {
+			udf_err(sb, "Partition %d is too long (%u)\n", p_index,
+				map->s_partition_len);
+			return -EFSCORRUPTED;
+		}
 		udf_debug("unallocSpaceBitmap (part %d) @ %u\n",
 			  p_index, bitmap->s_extPosition);
 	}