CVE-2026-68478

Summary

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.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/a4b9961efe8640f50800811b4a2b2046b3dc2ccc
• https://git.kernel.org/stable/c/8937b11f1c3896e066c3fb07387ba17bc8c50b8a
• https://git.kernel.org/stable/c/f1c675ecf6e5ad02722f0019f729d8bb588d502e
• https://git.kernel.org/stable/c/d5db3439ee8d1c165a09a47e984c4ba508c130df
• https://git.kernel.org/stable/c/b86666ac4009a252501cc17242582a7ec9ed976e
• https://git.kernel.org/stable/c/39151f0708c84221e94cdd6aa070aba5d7cb1c01
• https://git.kernel.org/stable/c/47f0c7d856c67c9935546d2644f18c0d0131b449
• https://git.kernel.org/stable/c/718178f524b98bc920d74bc771aed823c8b81425

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