CVE-2026-89755

/// Technical description

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

mm/migrate_device: clear stale mapping after freeing swapcache

__migrate_device_pages() reads the folio mapping before calling

folio_free_swap(). When folio_free_swap() succeeds, the folio is removed

from the swap cache, but the saved mapping still points to swap_space.

Passing the stale mapping to folio_migrate_mapping() makes it use the

mapped-folio path for a folio that is no longer in swapcache. It can then

operate on swap_space.i_pages with invalid reference accounting,

eventually triggering a folio reference count BUG.

After a successful split, nr still contains the number of pages in the

original large folio, although each resulting page is now a separate

order-0 folio. Reset nr to 1 so each split folio is processed separately,

including its own swapcache removal and mapping lookup.

Refresh the saved mapping after folio_free_swap() so the current folio

state is used during migration.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References