On Fri, Jan 15, 2021 at 08:49:40PM +0800, Muchun Song wrote:
> There is a race condition between __free_huge_page()
> and dissolve_free_huge_page().
>
> CPU0: CPU1:
>
> // page_count(page) == 1
> put_page(page)
> __free_huge_page(page)
> dissolve_free_huge_page(page)
> spin_lock(&hugetlb_lock)
> // PageHuge(page) && !page_count(page)
> update_and_free_page(page)
> // page is freed to the buddy
> spin_unlock(&hugetlb_lock)
> spin_lock(&hugetlb_lock)
> clear_page_huge_active(page)
> enqueue_huge_page(page)
> // It is wrong, the page is already freed
> spin_unlock(&hugetlb_lock)
>
> The race windows is between put_page() and dissolve_free_huge_page().
>
> We should make sure that the page is already on the free list
> when it is dissolved.
>
> As a result __free_huge_page would corrupt page(s) already in the buddy
> allocator.
>
> Fixes: c8721bbbdd36 ("mm: memory-hotplug: enable memory hotplug to handle
> hugepage")
> Signed-off-by: Muchun Song <[email protected]>
> Reviewed-by: Mike Kravetz <[email protected]>
> Cc: [email protected]
LGTM,
Reviewed-by: Oscar Salvador <[email protected]>
--
Oscar Salvador
SUSE L3
