CVE-2026-23097

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

migrate: correct lock ordering for hugetlb file folios

Syzbot has found a deadlock (analyzed by Lance Yang):

1) Task (5749): Holds folio_lock, then tries to acquire i_mmap_rwsem(read lock).

2) Task (5754): Holds i_mmap_rwsem(write lock), then tries to acquire

folio_lock.

migrate_pages()

-> migrate_hugetlbs()

-> unmap_and_move_huge_page() <- Takes folio_lock!

-> remove_migration_ptes()

-> __rmap_walk_file()

-> i_mmap_lock_read() <- Waits for i_mmap_rwsem(read lock)!

hugetlbfs_fallocate()

-> hugetlbfs_punch_hole() <- Takes i_mmap_rwsem(write lock)!

-> hugetlbfs_zero_partial_page()

-> filemap_lock_hugetlb_folio()

-> filemap_lock_folio()

-> __filemap_get_folio <- Waits for folio_lock!

The migration path is the one taking locks in the wrong order according to

the documentation at the top of mm/rmap.c. So expand the scope of the

existing i_mmap_lock to cover the calls to remove_migration_ptes() too.

This is (mostly) how it used to be after commit c0d0381ade79. That was

removed by 336bf30eb765 for both file & anon hugetlb pages when it should

only have been removed for anon hugetlb pages.