mm/migrate_device: clear stale mapping after freeing swapcache

Summary

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.

Timeline

1. Sep 11, 2026, 7:46 PM UTCCVE published
2. Oct 21, 2026, 12:48 PM UTCRecord last updated

Affected versions

• Linux Linux

  From df263d9a7dffee94ca5391120ee3b0587efa07f1 · fixed in 92db780dd644590c751246187e1229d5ac2e5544; From df263d9a7dffee94ca5391120ee3b0587efa07f1 · fixed in 4fa91f7bbc4135240b67daac03fc17d9e180a331; From df263d9a7dffee94ca5391120ee3b0587efa07f1 · fixed in 8ffedc6573a665cdc31ebe47eae7b32b78d0df83; From df263d9a7dffee94ca5391120ee3b0587efa07f1 · fixed in 34a00895d032a414830d41106a09329ae6c251b6

• Linux Linux

  6.6

• KernelLinux

  From 6.6.0 · fixed in 6.6.160; From 6.7.0 · fixed in 6.12.111; From 6.13.0 · fixed in 7.2.4

References 4