linux-kernel - Re: [PATCH 1/5] vfio/type1: Catch zero from pin_user_pages

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Message-ID: <CAHTA-uZK_1A1tNa_GWzy010C32wN=6ePoAp0hGZ7FToRsyr4iA@mail.gmail.com>
Date: Thu, 6 Feb 2025 19:38:12 -0600
From: Mitchell Augustin <mitchell.augustin@...onical.com>
To: Alex Williamson <alex.williamson@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org, peterx@...hat.com, 
	clg@...hat.com
Subject: Re: [PATCH 1/5] vfio/type1: Catch zero from pin_user_pages_remote()

Reviewed-by: "Mitchell Augustin" <mitchell.augustin@...onical.com>
Tested-by: "Mitchell Augustin" <mitchell.augustin@...onical.com>



On Wed, Feb 5, 2025 at 5:18 PM Alex Williamson
<alex.williamson@...hat.com> wrote:
>
> pin_user_pages_remote() can currently return zero for invalid args
> or zero nr_pages, neither of which should ever happen.  However
> vaddr_get_pfns() indicates it should only ever return a positive
> value or -errno and there's a theoretical case where this can slip
> through and be unhandled by callers.  Therefore convert zero to
> -EFAULT.
>
> Signed-off-by: Alex Williamson <alex.williamson@...hat.com>
> ---
>  drivers/vfio/vfio_iommu_type1.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
> index 50ebc9593c9d..119cf886d8c0 100644
> --- a/drivers/vfio/vfio_iommu_type1.c
> +++ b/drivers/vfio/vfio_iommu_type1.c
> @@ -564,6 +564,8 @@ static int vaddr_get_pfns(struct mm_struct *mm, unsigned long vaddr,
>         if (ret > 0) {
>                 *pfn = page_to_pfn(pages[0]);
>                 goto done;
> +       } else if (!ret) {
> +               ret = -EFAULT;
>         }
>
>         vaddr = untagged_addr_remote(mm, vaddr);
> --
> 2.47.1
>


--
Mitchell Augustin
Software Engineer - Ubuntu Partner Engineering