CVE-2026-90279md/raid5: round bitmap stripes with sector division

Official description

In the Linux kernel, the following vulnerability has been resolved: md/raid5: round bitmap stripes with sector division raid5_bitmap_sector_map() aligns the array range to full RAID5 stripe widths before converting it to component sectors. That width is chunk_sectors multiplied by the number of data disks, and it is not always a power of two. Reproduce with a 4-disk RAID5, 1024-sector chunks, and three data disks. The full-stripe width is 3072 sectors. For a one-sector write at array sector 3072, correct rounding gives array range [3072, 6144), which maps to component range [1024, 2048). The old round_down()/round_up() logic instead gives [1024, 4096), which maps to [0, 1024). Use sector_div() based arithmetic so the rounded range is aligned to the actual RAID5 stripe width. The deterministic mapper test now reports the fixed component range as [1024, 2048), while the old mask-based range was [0, 1024).

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/9d7490007707f90691911385365bd1d691d99225
• https://git.kernel.org/stable/c/cab7d949b18b2f1cd625689dc16c5f81236bac93
• https://git.kernel.org/stable/c/02c10581866d08822c6348e299881485fc546185
• https://git.kernel.org/stable/c/ccbdc483eb041eef809e9ff223d1ad63518a2c52
• https://git.kernel.org/stable/c/17ea021ae74987d6064c8195c4922fa025753892