CVE-2026-89614

In the Linux kernel, the following vulnerability has been resolved:

ntfs: bound the free-cluster bitmap scan to the volume

vol->lcn_empty_bits_per_page is sized from vol->nr_clusters at mount, but

ntfs_cluster_alloc() bounds its scan of that array by the size of $Bitmap.

Those are independent on-disk quantities and the mount-time check only

rejects a $Bitmap that is too small, so an image whose $Bitmap covers more

clusters than the volume has lets the scan index past the array. A run

whose LCN lies in that gap takes the allocator straight there, since the

caller passes the file's own last LCN as its locality hint. KASAN reports

a slab out-of-bounds read when a file on such a volume is extended.

Clamp the scan to what that array covers, mirroring the max_index

calculation the mount-time scan already uses, and reject a decoded LCN

at or beyond nr_clusters in the mapping pairs decoder. Conforming

volumes are unaffected.