linux-kernel - Re: [PATCH] media: videobuf2: Fix integer overrun in allocation

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Date:   Wed, 10 Mar 2021 08:58:39 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>
Cc:     Tomasz Figa <tfiga@...omium.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        stable@...r.kernel.org
Subject: Re: [PATCH] media: videobuf2: Fix integer overrun in allocation

Hi Laurent

On Wed, Mar 10, 2021 at 8:49 AM Laurent Pinchart
<laurent.pinchart@...asonboard.com> wrote:
>
> Hi Ricardo,
>
> Thank you for the patch.
Thank you!
>
> On Wed, Mar 10, 2021 at 12:43:17AM +0100, Ricardo Ribalda wrote:
> > The plane_length is an unsigned integer. So, if we have a size of
> > 0xffffffff bytes we incorrectly allocate 0 bytes instead of 1 << 32.
> >
> > Cc: stable@...r.kernel.org
> > Fixes: 7f8414594e47 ("[media] media: videobuf2: fix the length check for mmap")
> > Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
> > ---
> >  drivers/media/common/videobuf2/videobuf2-core.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c b/drivers/media/common/videobuf2/videobuf2-core.c
> > index 02281d13505f..543da515c761 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-core.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> > @@ -223,8 +223,10 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
> >        * NOTE: mmapped areas should be page aligned
> >        */
> >       for (plane = 0; plane < vb->num_planes; ++plane) {
> > +             unsigned long size = vb->planes[plane].length;
>
> unsigned long is still 32-bit on 32-bit platforms.
>
> > +
> >               /* Memops alloc requires size to be page aligned. */
> > -             unsigned long size = PAGE_ALIGN(vb->planes[plane].length);
> > +             size = PAGE_ALIGN(size);
> >
> >               /* Did it wrap around? */
> >               if (size < vb->planes[plane].length)
>
> Doesn't this address the issue already ?

Yes and no. If you need to allocate 0xffffffff you are still affected
by the underrun. The core will return an error instead of doing the
allocation.

(yes, I know it is a lot of memory for a buffer)

>
>
> --
> Regards,
>
> Laurent Pinchart



-- 
Ricardo Ribalda