CVE-2026-68478
Description
In the Linux kernel, the following vulnerability has been resolved:
memstick: ms_block: reject a card that reports too many blocks
msb_ftl_initialize() computes the zone count from the card block count
with no bound:
msb->zone_count = msb->block_count / MS_BLOCKS_IN_ZONE;
...
for (i = 0; i < msb->zone_count; i++)
msb->free_block_count[i] = MS_BLOCKS_IN_ZONE;
msb->block_count is a card value. msb_read_boot_blocks() reads
number_of_blocks from the card boot page and byte swaps it.
free_block_count is a fixed int[MS_MAX_ZONES]. MS_MAX_ZONES is 16, so the
valid indices are 0 to 15. The init loop above indexes it by zone_count.
msb_mark_block_used() and msb_mark_block_unused() index it by
pba / MS_BLOCKS_IN_ZONE, for pba up to block_count - 1. A card may report
up to 65535 blocks. A block_count above 8192 (MS_MAX_ZONES *
MS_BLOCKS_IN_ZONE) lets the pba index reach 16. That writes past
free_block_count[] and corrupts struct msb_data. A larger count runs the
init loop past the end too.
A real Memory Stick has at most 16 zones. So it has at most 8192 blocks.
msb_ftl_initialize() now rejects a card that reports more than
MS_MAX_ZONES * MS_BLOCKS_IN_ZONE blocks.