linux-kernel - Re: [PATCH] media: atomisp: Fixed error handling path

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Message-ID: <CAFqt6zZaf=+JcUuxKdoEj1vMs5MOsb1iYKStmwKiKLW8bbcnYQ@mail.gmail.com>
Date:   Tue, 29 Sep 2020 07:34:39 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     mchehab@...nel.org, sakari.ailus@...ux.intel.com,
        Greg KH <gregkh@...uxfoundation.org>,
        daniel.m.jordan@...cle.com,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michel Lespinasse <walken@...gle.com>, gustavoars@...nel.org,
        linux-media@...r.kernel.org,
        "open list:ANDROID DRIVERS" <devel@...verdev.osuosl.org>,
        linux-kernel@...r.kernel.org, John Hubbard <jhubbard@...dia.com>,
        Ira Weiny <ira.weiny@...el.com>
Subject: Re: [PATCH] media: atomisp: Fixed error handling path

Hi Dan,


On Mon, Sep 28, 2020 at 2:08 PM Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> On Sun, Sep 27, 2020 at 08:38:04PM +0530, Souptick Joarder wrote:
> > Inside alloc_user_pages() based on flag value either pin_user_pages()
> > or get_user_pages_fast() will be called. However, these API might fail.
> >
> > But free_user_pages() called in error handling path doesn't bother
> > about return value and will try to unpin bo->pgnr pages, which is
> > incorrect.
> >
> > Fix this by passing the page_nr to free_user_pages(). If page_nr > 0
> > pages will be unpinned based on bo->mem_type. This will also take care
> > of non error handling path.
> >
> > Fixes: 14a638ab96c5 ("media: atomisp: use pin_user_pages() for memory
> > allocation")
> > Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
> > Cc: John Hubbard <jhubbard@...dia.com>
> > Cc: Ira Weiny <ira.weiny@...el.com>
> > Cc: Dan Carpenter <dan.carpenter@...cle.com>
> > ---
> >  drivers/staging/media/atomisp/pci/hmm/hmm_bo.c | 13 ++++++++-----
> >  1 file changed, 8 insertions(+), 5 deletions(-)
> >
> > diff --git a/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c b/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c
> > index f13af23..0168f98 100644
> > --- a/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c
> > +++ b/drivers/staging/media/atomisp/pci/hmm/hmm_bo.c
> > @@ -857,16 +857,17 @@ static void free_private_pages(struct hmm_buffer_object *bo,
> >       kfree(bo->page_obj);
> >  }
> >
> > -static void free_user_pages(struct hmm_buffer_object *bo)
> > +static void free_user_pages(struct hmm_buffer_object *bo,
> > +                         unsigned int page_nr)
> >  {
> >       int i;
> >
> >       hmm_mem_stat.usr_size -= bo->pgnr;
>                               ^^^^^^^^^^^
> This is still a problem.  It needs to be hmm_mem_stat.usr_size -= page_nr.

In failure path, it is hmm_mem_stat.usr_size += bo->pgnr.
I think, hmm_mem_stat.usr_size -= bo->pgnr is correct as per existing code.
Do you think that needs to be changed ?

>
> regards,
> dan carpenter
>
> >
> >       if (bo->mem_type == HMM_BO_MEM_TYPE_PFN) {
> > -             unpin_user_pages(bo->pages, bo->pgnr);
> > +             unpin_user_pages(bo->pages, page_nr);
> >       } else {
> > -             for (i = 0; i < bo->pgnr; i++)
> > +             for (i = 0; i < page_nr; i++)
> >                       put_page(bo->pages[i]);
> >       }
> >       kfree(bo->pages);
>