linux-kernel - Re: [linux-next PATCH v3] drivers/virt/fsl

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Message-ID: <CAFqt6zaAWL-f9YnosMhy7oOh8wT48cPSrhrwxn4qGPspvFz-=w@mail.gmail.com>
Date:   Tue, 1 Sep 2020 03:40:30 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>,
        John Hubbard <jhubbard@...dia.com>
Cc:     Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        Arnd Bergmann <arnd@...db.de>, timur@...escale.com,
        galak@...nel.crashing.org, linux-kernel@...r.kernel.org
Subject: Re: [linux-next PATCH v3] drivers/virt/fsl_hypervisor: Fix error
 handling path

Hi John,

On Tue, Sep 1, 2020 at 3:38 AM Souptick Joarder <jrdr.linux@...il.com> wrote:
>
> First, when memory allocation for sg_list_unaligned failed, there
> is a bug of calling put_pages() as we haven't pinned any pages.
>
> Second, if get_user_pages_fast() failed we should unpinned num_pinned
> pages instead of checking till num_pages.
>
> This will address both.
>
> As part of these changes, minor update in documentation.
>
> Fixes: 6db7199407ca ("drivers/virt: introduce Freescale hypervisor
> management driver")
> Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>
> Reviewed-by: John Hubbard <jhubbard@...dia.com>

Few questions ->

First, there are minor updates from v2 -> v3 other than addressing your
review comments in v2. Would you like to review it again?

Second, I think, as per Documentation/core-api/pin_user_pages.rst,
this is case 5.
Shall I make the conversion as part of this series ?

> ---
> v2:
>    Added review tag.
>
> v3:
>    Address review comment on v2 from John.
>    Added review tag.
>
>  drivers/virt/fsl_hypervisor.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/virt/fsl_hypervisor.c b/drivers/virt/fsl_hypervisor.c
> index 1b0b11b..efb4e7f 100644
> --- a/drivers/virt/fsl_hypervisor.c
> +++ b/drivers/virt/fsl_hypervisor.c
> @@ -157,7 +157,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>
>         unsigned int i;
>         long ret = 0;
> -       int num_pinned; /* return value from get_user_pages() */
> +       int num_pinned = 0; /* return value from get_user_pages_fast() */
>         phys_addr_t remote_paddr; /* The next address in the remote buffer */
>         uint32_t count; /* The number of bytes left to copy */
>
> @@ -174,7 +174,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>                 return -EINVAL;
>
>         /*
> -        * The array of pages returned by get_user_pages() covers only
> +        * The array of pages returned by get_user_pages_fast() covers only
>          * page-aligned memory.  Since the user buffer is probably not
>          * page-aligned, we need to handle the discrepancy.
>          *
> @@ -224,7 +224,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>
>         /*
>          * 'pages' is an array of struct page pointers that's initialized by
> -        * get_user_pages().
> +        * get_user_pages_fast().
>          */
>         pages = kcalloc(num_pages, sizeof(struct page *), GFP_KERNEL);
>         if (!pages) {
> @@ -241,7 +241,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>         if (!sg_list_unaligned) {
>                 pr_debug("fsl-hv: could not allocate S/G list\n");
>                 ret = -ENOMEM;
> -               goto exit;
> +               goto free_pages;
>         }
>         sg_list = PTR_ALIGN(sg_list_unaligned, sizeof(struct fh_sg_list));
>
> @@ -250,7 +250,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>                 num_pages, param.source != -1 ? FOLL_WRITE : 0, pages);
>
>         if (num_pinned != num_pages) {
> -               /* get_user_pages() failed */
> +               /* get_user_pages_fast() failed */
>                 pr_debug("fsl-hv: could not lock source buffer\n");
>                 ret = (num_pinned < 0) ? num_pinned : -EFAULT;
>                 goto exit;
> @@ -293,12 +293,12 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
>
>  exit:
>         if (pages) {
> -               for (i = 0; i < num_pages; i++)
> -                       if (pages[i])
> -                               put_page(pages[i]);
> +               for (i = 0; i < num_pinned; i++)
> +                       put_page(pages[i]);
>         }
>
>         kfree(sg_list_unaligned);
> +free_pages:
>         kfree(pages);
>
>         if (!ret)
> --
> 1.9.1
>