Re: [PATCH] mm/migrate_device: fix pgtable leak in migrate_vma_insert_huge_pmd_page

[Huang, Ying]

Hi, Sunny,

Thanks for working on this!

Sunny Patel <nueralspacetech@xxxxxxxxx> writes:

> When migrate_vma_insert_huge_pmd_page() jumps to unlock_abort due
> to a PMD check failure, the pgtable allocated earlier via
> pte_alloc_one() is never freed, causing a memory leak.
>
> Add a pte_free() call in the unlock_abort error path to release
> the pgtable before returning.
>
> Signed-off-by: Sunny Patel <nueralspacetech@xxxxxxxxx>
> ---
>  mm/migrate_device.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/mm/migrate_device.c b/mm/migrate_device.c
> index fbfe5715f635..457bab5c7c31 100644
> --- a/mm/migrate_device.c
> +++ b/mm/migrate_device.c
> @@ -893,6 +893,7 @@ static int migrate_vma_insert_huge_pmd_page(struct migrate_vma *migrate,
>  
>  unlock_abort:
>  	spin_unlock(ptl);
> +	pte_free(vma->vm_mm, pgtable);
>  abort:
>  	for (i = 0; i < HPAGE_PMD_NR; i++)
>  		src[i] &= ~MIGRATE_PFN_MIGRATE;

Is it better to use guard based automatic memory freeing?

And check whether guard can help unlock case too?

---
Best Regards,
Huang, Ying