linux-kernel - Re: [PATCH v2] media: videobuf2: Fix IS_ERR checking in vb2_vmalloc_put

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Message-ID: <CAAFQd5A4w5N4GwdJ0x+Rw=EM_J1Nf=6M2XmUi-ZcoyW5L8J-zg@mail.gmail.com>
Date:   Thu, 12 Oct 2023 15:17:31 +0900
From:   Tomasz Figa <tfiga@...omium.org>
To:     Ma Ke <make_ruc2021@....com>
Cc:     m.szyprowski@...sung.com, mchehab@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] media: videobuf2: Fix IS_ERR checking in vb2_vmalloc_put_userptr()

On Tue, Oct 3, 2023 at 6:13 PM Ma Ke <make_ruc2021@....com> wrote:
>
> In order to avoid error pointers from frame_vector_pages(), we could
> use IS_ERR() to check the return value to fix this. This checking
> operation could make sure that vector contains pages.
>
> Signed-off-by: Ma Ke <make_ruc2021@....com>
> ---
>  drivers/media/common/videobuf2/videobuf2-vmalloc.c | 10 ++++++----
>  1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/media/common/videobuf2/videobuf2-vmalloc.c b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> index 7c635e292106..5aa66305546d 100644
> --- a/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> +++ b/drivers/media/common/videobuf2/videobuf2-vmalloc.c
> @@ -133,13 +133,15 @@ static void vb2_vmalloc_put_userptr(void *buf_priv)
>
>         if (!buf->vec->is_pfns) {
>                 n_pages = frame_vector_count(buf->vec);
> -               pages = frame_vector_pages(buf->vec);
>                 if (vaddr)
>                         vm_unmap_ram((void *)vaddr, n_pages);
>                 if (buf->dma_dir == DMA_FROM_DEVICE ||
> -                   buf->dma_dir == DMA_BIDIRECTIONAL)
> -                       for (i = 0; i < n_pages; i++)
> -                               set_page_dirty_lock(pages[i]);
> +                   buf->dma_dir == DMA_BIDIRECTIONAL){

Missing space between ) and { .

> +                       pages = frame_vector_pages(buf->vec);
> +                       if (!WARN_ON_ONCE(IS_ERR(pages)))

I still think this cannot happen, but the frame vector code is a mess,
so being a bit more defensive here is probably fine, until someone can
clean up that code (probably by removing the PFN-only code path
completely).

> +                               for (i = 0; i < n_pages; i++)
> +                                       set_page_dirty_lock(pages[i]);
> +               }
>         } else {
>                 iounmap((__force void __iomem *)buf->vaddr);
>         }
> --
> 2.37.2
>

With that one formatting issue fixed: (Mauro, Hans, maybe it could be
fixed up when applying?)

Acked-by: Tomasz Figa <tfiga@...omium.org>

Best regards,
Tomasz