linux-kernel - Re: [PATCH 3.16 025/305] media: uvcvideo: Fix uvc_alloc

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Date:   Fri, 7 Jun 2019 08:09:27 -0700
From:   Doug Anderson <dianders@...omium.org>
To:     "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Denis Kirjanov <kda@...ux-powerpc.org>,
        Nadav Amit <namit@...are.com>,
        Mauro Carvalho Chehab <mchehab+samsung@...nel.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Ben Hutchings <ben@...adent.org.uk>,
        Tomasz Figa <tfiga@...omium.org>,
        Guenter Roeck <groeck@...omium.org>
Subject: Re: [PATCH 3.16 025/305] media: uvcvideo: Fix uvc_alloc_entity()
 allocation alignment

Hi,

On Sun, Feb 3, 2019 at 5:50 AM Ben Hutchings <ben@...adent.org.uk> wrote:
>
> 3.16.63-rc1 review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Nadav Amit <namit@...are.com>
>
> commit 89dd34caf73e28018c58cd193751e41b1f8bdc56 upstream.
>
> The use of ALIGN() in uvc_alloc_entity() is incorrect, since the size of
> (entity->pads) is not a power of two. As a stop-gap, until a better
> solution is adapted, use roundup() instead.
>
> Found by a static assertion. Compile-tested only.
>
> Fixes: 4ffc2d89f38a ("uvcvideo: Register subdevices for each entity")
>
> Signed-off-by: Nadav Amit <namit@...are.com>
> Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@...nel.org>
> Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
> ---
>  drivers/media/usb/uvc/uvc_driver.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> --- a/drivers/media/usb/uvc/uvc_driver.c
> +++ b/drivers/media/usb/uvc/uvc_driver.c
> @@ -826,7 +826,7 @@ static struct uvc_entity *uvc_alloc_enti
>         unsigned int size;
>         unsigned int i;
>
> -       extra_size = ALIGN(extra_size, sizeof(*entity->pads));
> +       extra_size = roundup(extra_size, sizeof(*entity->pads));
>         num_inputs = (type & UVC_TERM_OUTPUT) ? num_pads : num_pads - 1;
>         size = sizeof(*entity) + extra_size + sizeof(*entity->pads) * num_pads
>              + num_inputs;

Funny that this commit made its way to 3.16 but didn't make its way to
4.19 (at least checking 4.19.43).  I haven't seen any actual crashes
caused by the lack of this commit but it seems like the kind of thing
we probably want picked back to other stable kernels too.

-Doug