linux-kernel - Re: [PATCH v2] drivers/virt/fsl_hypervisor: Correcting error handling path

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Date:   Wed, 26 Aug 2020 01:50:15 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     John Hubbard <jhubbard@...dia.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Jason Gunthorpe <jgg@...pe.ca>,
        Dan Williams <dan.j.williams@...el.com>,
        Greg KH <gregkh@...uxfoundation.org>,
        mchehab+samsung@...nel.org, linux-kernel@...r.kernel.org,
        Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH v2] drivers/virt/fsl_hypervisor: Correcting error handling path

On Thu, Jul 30, 2020 at 6:30 AM John Hubbard <jhubbard@...dia.com> wrote:
>
> On 7/29/20 12:01 PM, Souptick Joarder wrote:
> > First, when memory allocation for sg_list_unaligned failed, there
> > is no point of calling put_pages() as we haven't pinned any pages.
> >
> > Second, if get_user_pages_fast() failed we should unpinned num_pinned
> > pages, no point of checking till num_pages.
>
> Hi Souptick,
>
> For both of the above, the wording "no point" is so overly gentle as
> to be misleading. That's because calling put_page() on any pages beyond
> num_pinned is a *bug*.
>
> So let's reword that. And let's change the patch subject from "Correcting" to
> "fix".
>
> And probably good to add a Fixes: tag, too.

Is there any scripts/ settings to fetch Fixes: tag other than using git blame ?

>
> More:
>
> >
> > This will address both.
> >
> > Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> > Reviewed-by: Dan Carpenter <dan.carpenter@...cle.com>
> > Cc: John Hubbard <jhubbard@...dia.com>
> > ---
> > v2:
> >       Added review tag.
> >
> >   drivers/virt/fsl_hypervisor.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/virt/fsl_hypervisor.c b/drivers/virt/fsl_hypervisor.c
> > index 1b0b11b..ea344d7 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() */
> >       phys_addr_t remote_paddr; /* The next address in the remote buffer */
> >       uint32_t count; /* The number of bytes left to copy */
> >
> > @@ -293,7 +293,7 @@ static long ioctl_memcpy(struct fsl_hv_ioctl_memcpy __user *p)
> >
> >   exit:
> >       if (pages) {
> > -             for (i = 0; i < num_pages; i++)
> > +             for (i = 0; i < num_pinned; i++)
> >                       if (pages[i])
>
> I suspect that this "if" is unnecessary now.
>
> Either way, the diff itself looks good to me, so with the wording changes to
> the commit description, you can add:
>
>      Reviewed-by: John Hubbard <jhubbard@...dia.com>
>
> thanks,
> --
> John Hubbard
> NVIDIA
>
> >                               put_page(pages[i]);
> >       }
> >
>