linux-kernel - Re: [PATCH 02/38] media: v4l2-ioctl: avoid memory leaks on some time32 compat functions

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Date:   Wed, 2 Sep 2020 19:26:12 +0300
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Cc:     Hans Verkuil <hverkuil-cisco@...all.nl>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        Arnd Bergmann <arnd@...db.de>,
        Vandana BN <bnvandana@...il.com>,
        Niklas Söderlund 
        <niklas.soderlund+renesas@...natech.se>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 02/38] media: v4l2-ioctl: avoid memory leaks on some
 time32 compat functions

Hi Mauro,

Thank you for the patch.

On Wed, Sep 02, 2020 at 06:10:05PM +0200, Mauro Carvalho Chehab wrote:
> There are some reports about possible memory leaks:
> 
> 	drivers/media/v4l2-core//v4l2-ioctl.c:3203 video_put_user() warn: check that 'ev32' doesn't leak information (struct has a hole after 'type')
> 	drivers/media/v4l2-core//v4l2-ioctl.c:3230 video_put_user() warn: check that 'vb32' doesn't leak information (struct has a hole after 'memory')
> 
> While smatch seems to be reporting a false positive (line 3203),
> there's indeed a possible leak with reserved2 at vb32.
> 
> We might have fixed just that one, but smatch checks won't
> be able to check leaks at ev32. So, re-work the code in a way
> that will ensure that the var contents will be zeroed before
> filling it.
> 
> With that, we don't need anymore to touch reserved fields.
> 
> Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
> ---
>  drivers/media/v4l2-core/v4l2-ioctl.c | 48 ++++++++++++++--------------
>  1 file changed, 24 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index a556880f225a..6f3fe9c4b64a 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -3189,17 +3189,16 @@ static int video_put_user(void __user *arg, void *parg, unsigned int cmd)
>  #ifdef CONFIG_COMPAT_32BIT_TIME
>  	case VIDIOC_DQEVENT_TIME32: {
>  		struct v4l2_event *ev = parg;
> -		struct v4l2_event_time32 ev32 = {
> -			.type		= ev->type,
> -			.pending	= ev->pending,
> -			.sequence	= ev->sequence,
> -			.timestamp.tv_sec  = ev->timestamp.tv_sec,
> -			.timestamp.tv_nsec = ev->timestamp.tv_nsec,
> -			.id		= ev->id,
> -		};
> +		struct v4l2_event_time32 ev32;
>  
> +		memset(&ev32, 0, sizeof(ev32));
> +		ev32.type		= ev->type,

The lines should end with ';', not ','.

With this fixed,

Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>

> +		ev32.pending		= ev->pending,
> +		ev32.sequence		= ev->sequence,
> +		ev32.timestamp.tv_sec	= ev->timestamp.tv_sec,
> +		ev32.timestamp.tv_nsec	= ev->timestamp.tv_nsec,
> +		ev32.id			= ev->id,
>  		memcpy(&ev32.u, &ev->u, sizeof(ev->u));
> -		memcpy(&ev32.reserved, &ev->reserved, sizeof(ev->reserved));
>  
>  		if (copy_to_user(arg, &ev32, sizeof(ev32)))
>  			return -EFAULT;
> @@ -3210,21 +3209,22 @@ static int video_put_user(void __user *arg, void *parg, unsigned int cmd)
>  	case VIDIOC_DQBUF_TIME32:
>  	case VIDIOC_PREPARE_BUF_TIME32: {
>  		struct v4l2_buffer *vb = parg;
> -		struct v4l2_buffer_time32 vb32 = {
> -			.index		= vb->index,
> -			.type		= vb->type,
> -			.bytesused	= vb->bytesused,
> -			.flags		= vb->flags,
> -			.field		= vb->field,
> -			.timestamp.tv_sec	= vb->timestamp.tv_sec,
> -			.timestamp.tv_usec	= vb->timestamp.tv_usec,
> -			.timecode	= vb->timecode,
> -			.sequence	= vb->sequence,
> -			.memory		= vb->memory,
> -			.m.userptr	= vb->m.userptr,
> -			.length		= vb->length,
> -			.request_fd	= vb->request_fd,
> -		};
> +		struct v4l2_buffer_time32 vb32;
> +
> +		memset(&vb32, 0, sizeof(vb32));
> +		vb32.index		= vb->index,
> +		vb32.type		= vb->type,
> +		vb32.bytesused		= vb->bytesused,
> +		vb32.flags		= vb->flags,
> +		vb32.field		= vb->field,
> +		vb32.timestamp.tv_sec	= vb->timestamp.tv_sec,
> +		vb32.timestamp.tv_usec	= vb->timestamp.tv_usec,
> +		vb32.timecode		= vb->timecode,
> +		vb32.sequence		= vb->sequence,
> +		vb32.memory		= vb->memory,
> +		vb32.length		= vb->length,
> +		vb32.request_fd		= vb->request_fd,
> +		memcpy(&vb32.m, &vb->m, sizeof(vb->m));
>  
>  		if (copy_to_user(arg, &vb32, sizeof(vb32)))
>  			return -EFAULT;

-- 
Regards,

Laurent Pinchart