On Thu, Dec 13, 2018 at 02:49:44PM +0200, Laurent Pinchart wrote:
> Hi Sakari,
>
> Thank you for the patch.
>
> On Thursday, 13 December 2018 12:40:04 EET Sakari Ailus wrote:
> > PAGE_ALIGN() may wrap the buffer size around to 0. Prevent this by
> > checking that the aligned value is not smaller than the unaligned one.
> >
> > Note on backporting to stable: the file used to be under
> > drivers/media/v4l2-core, it was moved to the current location after 4.14.
> >
> > Signed-off-by: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> > drivers/media/common/videobuf2/videobuf2-core.c | 4 ++++
> > 1 file changed, 4 insertions(+)
> >
> > diff --git a/drivers/media/common/videobuf2/videobuf2-core.c
> > b/drivers/media/common/videobuf2/videobuf2-core.c index
> > 0ca81d495bdaf..0234ddbfa4de2 100644
> > --- a/drivers/media/common/videobuf2/videobuf2-core.c
> > +++ b/drivers/media/common/videobuf2/videobuf2-core.c
> > @@ -207,6 +207,10 @@ static int __vb2_buf_mem_alloc(struct vb2_buffer *vb)
> > for (plane = 0; plane < vb->num_planes; ++plane) {
> > unsigned long size = PAGE_ALIGN(vb->planes[plane].length);
> >
> > + /* Did it wrap around? */
> > + if (size < vb->planes[plane].length)
> > + goto free;
> > +
> > mem_priv = call_ptr_memop(vb, alloc,
> > q->alloc_devs[plane] ? : q->dev,
> > q->dma_attrs, size, q->dma_dir, q->gfp_flags);
>
> Wouldn't it be better to reject length > INT_MAX (or some variations of that)
> a few steps before, for instance just before calling __vb2_queue_alloc() ?
> There's already a check in vb2_core_reqbufs():
>
> /* Check that driver has set sane values */
> if (WARN_ON(!num_planes))
> return -EINVAL;
>
> for (i = 0; i < num_planes; i++)
> if (WARN_ON(!plane_sizes[i]))
> return -EINVAL;
>
> It could be extended to validate the sizes against wrap-around, and moved to a
> separate function to be called in vb2_core_create_bufs() as well (as those
> checks are missing there). Alternatively, the checks could be moved to the
> beginning of __vb2_queue_alloc().
I'd hate to distribute the aligning to PAGE_SIZE in the two functions. An
alternative would be to add a new function argument for the aligned size,
but I like that even less. I think it might be better as-is.
I don't have a strong opinion either way though, and you certainly have a
point as well. What do you think?
--
Sakari Ailus
sakari.ailus@xxxxxxxxxxxxxxx
