In the Linux kernel, the following vulnerability has been resolved: udf: validate sparing table length as an entry count, not a byte count udf_load_sparable_map() accepts a sparing table when sizeof(*st) + le16_to_cpu(st-reallocationTableLen) > sb-s_blocksize is false, i.e. it treats reallocationTableLen as a number of BYTES that must fit in the block. But the table is walked as an array of 8-byte sparingEntry elements: for (i = 0.

i < le16_to_cpu(st-reallocationTableLen)

i++) { struct sparingEntry entry = &st-mapEntry[i]; ... entry-origLocation ... } in udf_get_pblock_spar15() and udf_relocate_blocks(). A reallocationTableLen of N therefore passes the check whenever sizeof(st) + N <= blocksize, yet the consumers index sizeof(st) + N sizeof(struct sparingEntry) bytes -- up to ~8x the block. On a crafted UDF image this is an out-of-bounds read in udf_get_pblock_spar15()

udf_relocate_blocks() additionally feeds the same length to udf_update_tag(), whose crc_itu_t() reads far past the block, and its memmove() through st-mapEntry[] is an out-of-bounds write. Validate reallocationTableLen as the entry count it is, with struct_size().