linux-kernel - Re: [PATCH] media: uvcvideo: Fix a memory leak in an error handling path of 'uvc_ioctl_ctrl

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Date:   Thu, 11 Nov 2021 11:40:32 +0100
From:   Ricardo Ribalda <ribalda@...omium.org>
To:     Dan Carpenter <dan.carpenter@...cle.com>
Cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        laurent.pinchart@...asonboard.com, mchehab@...nel.org,
        hverkuil-cisco@...all.nl, linux-media@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] media: uvcvideo: Fix a memory leak in an error handling
 path of 'uvc_ioctl_ctrl_map()'

I belive this is also addressed by this patch that is under review:

https://patchwork.linuxtv.org/project/linux-media/patch/20211008120914.69175-1-ribalda@chromium.org/

On Thu, 11 Nov 2021 at 11:33, Dan Carpenter <dan.carpenter@...cle.com> wrote:
>
> On Thu, Nov 11, 2021 at 09:06:11AM +0100, Christophe JAILLET wrote:
> > If 'map->name' can't be allocated, 'map' must be released before returning.
> >
> > Fixes: 70fa906d6fce ("media: uvcvideo: Use control names from framework")
> > Signed-off-by: Christophe JAILLET <christophe.jaillet@...adoo.fr>
> > ---
> >  drivers/media/usb/uvc/uvc_v4l2.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> > index f4e4aff8ddf7..5aa76a9a6080 100644
> > --- a/drivers/media/usb/uvc/uvc_v4l2.c
> > +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> > @@ -44,8 +44,10 @@ static int uvc_ioctl_ctrl_map(struct uvc_video_chain *chain,
> >       if (v4l2_ctrl_get_name(map->id) == NULL) {
> >               map->name = kmemdup(xmap->name, sizeof(xmap->name),
> >                                   GFP_KERNEL);
> > -             if (!map->name)
> > +             if (!map->name) {
> > +                     kfree(map);
> >                       return -ENOMEM;
> > +             }
>
> Your patch is fine but there is a second issue.  The error handling
> should free "map->name" as well.  The problem is that this function
> frees everything on the success path at all, but freeing map->name on
> the success path will lead to a crash so you have to do something
> weird like:
>
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index f4e4aff8ddf7..953a5cbf7945 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -90,6 +90,9 @@ static int uvc_ioctl_ctrl_map(struct uvc_video_chain *chain,
>         ret = uvc_ctrl_add_mapping(chain, map);
>
>         kfree(map->menu_info);
> +free_name:
> +       if (ret)
> +               kfree(map->name);
>  free_map:
>         kfree(map);
>
>


-- 
Ricardo Ribalda