[PATCH] media: uvcvideo: fix division by zero at stream start

[PATCH] media: uvcvideo: fix division by zero at stream start

[Johan Hovold]

Add the missing bulk-endpoint max-packet sanity check to probe() to
avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
device has broken descriptors (or when doing descriptor fuzz testing).

Note that USB core will reject URBs submitted for endpoints with zero
wMaxPacketSize but that drivers doing packet-size calculations still
need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
endpoint descriptors with maxpacket=0")).

Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
Cc: stable@vger.kernel.org      # 2.6.26
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/media/usb/uvc/uvc_video.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
index e16464606b14..85ac5c1081b6 100644
--- a/drivers/media/usb/uvc/uvc_video.c
+++ b/drivers/media/usb/uvc/uvc_video.c
@@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
 		if (ep == NULL)
 			return -EIO;
 
+		/* Reject broken descriptors. */
+		if (usb_endpoint_maxp(&ep->desc) == 0)
+			return -EIO;
+
 		ret = uvc_init_video_bulk(stream, ep, gfp_flags);
 	}
 
-- 
2.32.0

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Kieran Bingham]

Quoting Johan Hovold (2021-10-26 10:55:11)
> Add the missing bulk-endpoint max-packet sanity check to probe() to
> avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
> device has broken descriptors (or when doing descriptor fuzz testing).
> 
> Note that USB core will reject URBs submitted for endpoints with zero
> wMaxPacketSize but that drivers doing packet-size calculations still
> need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> endpoint descriptors with maxpacket=0")).
> 
> Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> Cc: stable@vger.kernel.org      # 2.6.26
> Signed-off-by: Johan Hovold <johan@kernel.org>
> ---
>  drivers/media/usb/uvc/uvc_video.c | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index e16464606b14..85ac5c1081b6 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
>                 if (ep == NULL)
>                         return -EIO;
>  
> +               /* Reject broken descriptors. */
> +               if (usb_endpoint_maxp(&ep->desc) == 0)
> +                       return -EIO;

Is there any value in identifying this with a specific return code like
-ENODATA?

But either way, this seems sane.

Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>

> +
>                 ret = uvc_init_video_bulk(stream, ep, gfp_flags);
>         }
>  
> -- 
> 2.32.0
>

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Laurent Pinchart]

On Tue, Oct 26, 2021 at 11:55:05AM +0100, Kieran Bingham wrote:
> Quoting Johan Hovold (2021-10-26 10:55:11)
> > Add the missing bulk-endpoint max-packet sanity check to probe() to
> > avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
> > device has broken descriptors (or when doing descriptor fuzz testing).
> > 
> > Note that USB core will reject URBs submitted for endpoints with zero
> > wMaxPacketSize but that drivers doing packet-size calculations still
> > need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> > endpoint descriptors with maxpacket=0")).
> > 
> > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > Cc: stable@vger.kernel.org      # 2.6.26
> > Signed-off-by: Johan Hovold <johan@kernel.org>
> > ---
> >  drivers/media/usb/uvc/uvc_video.c | 4 ++++
> >  1 file changed, 4 insertions(+)
> > 
> > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > index e16464606b14..85ac5c1081b6 100644
> > --- a/drivers/media/usb/uvc/uvc_video.c
> > +++ b/drivers/media/usb/uvc/uvc_video.c
> > @@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
> >                 if (ep == NULL)
> >                         return -EIO;
> >  
> > +               /* Reject broken descriptors. */
> > +               if (usb_endpoint_maxp(&ep->desc) == 0)
> > +                       return -EIO;
> 
> Is there any value in identifying this with a specific return code like
> -ENODATA?

Going one step further, wouldn't it be better to fail probe() for those
devices ?

> But either way, this seems sane.
> 
> Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
> 
> > +
> >                 ret = uvc_init_video_bulk(stream, ep, gfp_flags);
> >         }
> >  

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Johan Hovold]

On Tue, Oct 26, 2021 at 02:15:20PM +0300, Laurent Pinchart wrote:
> On Tue, Oct 26, 2021 at 11:55:05AM +0100, Kieran Bingham wrote:
> > Quoting Johan Hovold (2021-10-26 10:55:11)
> > > Add the missing bulk-endpoint max-packet sanity check to probe() to
> > > avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
> > > device has broken descriptors (or when doing descriptor fuzz testing).
> > > 
> > > Note that USB core will reject URBs submitted for endpoints with zero
> > > wMaxPacketSize but that drivers doing packet-size calculations still
> > > need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> > > endpoint descriptors with maxpacket=0")).
> > > 
> > > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > > Cc: stable@vger.kernel.org      # 2.6.26
> > > Signed-off-by: Johan Hovold <johan@kernel.org>
> > > ---
> > >  drivers/media/usb/uvc/uvc_video.c | 4 ++++
> > >  1 file changed, 4 insertions(+)
> > > 
> > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > index e16464606b14..85ac5c1081b6 100644
> > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > @@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
> > >                 if (ep == NULL)
> > >                         return -EIO;
> > >  
> > > +               /* Reject broken descriptors. */
> > > +               if (usb_endpoint_maxp(&ep->desc) == 0)
> > > +                       return -EIO;
> > 
> > Is there any value in identifying this with a specific return code like
> > -ENODATA?
> 
> Going one step further, wouldn't it be better to fail probe() for those
> devices ?

This is not how the driver works today. Look at the "return -EIO" just
above in case the expected endpoint is missing. And similarly for the
isochronous case for which zero wMaxPacket isn't handled until
uvc_video_start_transfer() either (a few lines further up still).

Note however the copy-paste error in the commit message mentioning
probe(), which is indeed where this would typically be handled.

Do you want me to resend or can you change

	s/probe()/uvc_video_start_transfer()/

in the commit message when applying if you think this is acceptable as
is?

Johan

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Laurent Pinchart]

Hi Johan,

On Tue, Oct 26, 2021 at 02:06:55PM +0200, Johan Hovold wrote:
> On Tue, Oct 26, 2021 at 02:15:20PM +0300, Laurent Pinchart wrote:
> > On Tue, Oct 26, 2021 at 11:55:05AM +0100, Kieran Bingham wrote:
> > > Quoting Johan Hovold (2021-10-26 10:55:11)
> > > > Add the missing bulk-endpoint max-packet sanity check to probe() to
> > > > avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
> > > > device has broken descriptors (or when doing descriptor fuzz testing).
> > > > 
> > > > Note that USB core will reject URBs submitted for endpoints with zero
> > > > wMaxPacketSize but that drivers doing packet-size calculations still
> > > > need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> > > > endpoint descriptors with maxpacket=0")).
> > > > 
> > > > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > > > Cc: stable@vger.kernel.org      # 2.6.26
> > > > Signed-off-by: Johan Hovold <johan@kernel.org>
> > > > ---
> > > >  drivers/media/usb/uvc/uvc_video.c | 4 ++++
> > > >  1 file changed, 4 insertions(+)
> > > > 
> > > > diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> > > > index e16464606b14..85ac5c1081b6 100644
> > > > --- a/drivers/media/usb/uvc/uvc_video.c
> > > > +++ b/drivers/media/usb/uvc/uvc_video.c
> > > > @@ -1958,6 +1958,10 @@ static int uvc_video_start_transfer(struct uvc_streaming *stream,
> > > >                 if (ep == NULL)
> > > >                         return -EIO;
> > > >  
> > > > +               /* Reject broken descriptors. */
> > > > +               if (usb_endpoint_maxp(&ep->desc) == 0)
> > > > +                       return -EIO;
> > > 
> > > Is there any value in identifying this with a specific return code like
> > > -ENODATA?
> > 
> > Going one step further, wouldn't it be better to fail probe() for those
> > devices ?
> 
> This is not how the driver works today. Look at the "return -EIO" just
> above in case the expected endpoint is missing. And similarly for the
> isochronous case for which zero wMaxPacket isn't handled until
> uvc_video_start_transfer() either (a few lines further up still).

That's a good point, it wouldn't be reasonable to ask you to fix all
that :-)

> Note however the copy-paste error in the commit message mentioning
> probe(), which is indeed where this would typically be handled.
> 
> Do you want me to resend or can you change
> 
> 	s/probe()/uvc_video_start_transfer()/
> 
> in the commit message when applying if you think this is acceptable as
> is?

I can fix this when applying.

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

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Johan Hovold]

On Wed, Oct 27, 2021 at 12:50:46AM +0300, Laurent Pinchart wrote:
> Hi Johan,
> 
> On Tue, Oct 26, 2021 at 02:06:55PM +0200, Johan Hovold wrote:

> > Do you want me to resend or can you change
> > 
> > 	s/probe()/uvc_video_start_transfer()/
> > 
> > in the commit message when applying if you think this is acceptable as
> > is?
> 
> I can fix this when applying.

Perfect, thanks.

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

Johan

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Johan Hovold]

Hi Laurent,

On Wed, Oct 27, 2021 at 12:50:46AM +0300, Laurent Pinchart wrote:
> Hi Johan,
> 
> On Tue, Oct 26, 2021 at 02:06:55PM +0200, Johan Hovold wrote:
> > On Tue, Oct 26, 2021 at 02:15:20PM +0300, Laurent Pinchart wrote:
> > > On Tue, Oct 26, 2021 at 11:55:05AM +0100, Kieran Bingham wrote:
> > > > Quoting Johan Hovold (2021-10-26 10:55:11)
> > > > > Add the missing bulk-endpoint max-packet sanity check to probe() to
> > > > > avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
> > > > > device has broken descriptors (or when doing descriptor fuzz testing).
> > > > > 
> > > > > Note that USB core will reject URBs submitted for endpoints with zero
> > > > > wMaxPacketSize but that drivers doing packet-size calculations still
> > > > > need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> > > > > endpoint descriptors with maxpacket=0")).
> > > > > 
> > > > > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > > > > Cc: stable@vger.kernel.org      # 2.6.26
> > > > > Signed-off-by: Johan Hovold <johan@kernel.org>

> > Note however the copy-paste error in the commit message mentioning
> > probe(), which is indeed where this would typically be handled.
> > 
> > Do you want me to resend or can you change
> > 
> > 	s/probe()/uvc_video_start_transfer()/
> > 
> > in the commit message when applying if you think this is acceptable as
> > is?
> 
> I can fix this when applying.
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

I noticed that this one hasn't showed up in linux-next yet. Do you still
have it in your queue or do you want me to resend?

Johan

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Laurent Pinchart]

Hi Johan,

On Fri, Dec 03, 2021 at 11:29:07AM +0100, Johan Hovold wrote:
> On Wed, Oct 27, 2021 at 12:50:46AM +0300, Laurent Pinchart wrote:
> > On Tue, Oct 26, 2021 at 02:06:55PM +0200, Johan Hovold wrote:
> > > On Tue, Oct 26, 2021 at 02:15:20PM +0300, Laurent Pinchart wrote:
> > > > On Tue, Oct 26, 2021 at 11:55:05AM +0100, Kieran Bingham wrote:
> > > > > Quoting Johan Hovold (2021-10-26 10:55:11)
> > > > > > Add the missing bulk-endpoint max-packet sanity check to probe() to
> > > > > > avoid division by zero in uvc_alloc_urb_buffers() in case a malicious
> > > > > > device has broken descriptors (or when doing descriptor fuzz testing).
> > > > > > 
> > > > > > Note that USB core will reject URBs submitted for endpoints with zero
> > > > > > wMaxPacketSize but that drivers doing packet-size calculations still
> > > > > > need to handle this (cf. commit 2548288b4fb0 ("USB: Fix: Don't skip
> > > > > > endpoint descriptors with maxpacket=0")).
> > > > > > 
> > > > > > Fixes: c0efd232929c ("V4L/DVB (8145a): USB Video Class driver")
> > > > > > Cc: stable@vger.kernel.org      # 2.6.26
> > > > > > Signed-off-by: Johan Hovold <johan@kernel.org>
> > >
> > > Note however the copy-paste error in the commit message mentioning
> > > probe(), which is indeed where this would typically be handled.
> > > 
> > > Do you want me to resend or can you change
> > > 
> > > 	s/probe()/uvc_video_start_transfer()/
> > > 
> > > in the commit message when applying if you think this is acceptable as
> > > is?
> > 
> > I can fix this when applying.
> > 
> > Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> 
> I noticed that this one hasn't showed up in linux-next yet. Do you still
> have it in your queue or do you want me to resend?

It should be in Mauro's queue now:

https://lore.kernel.org/all/YacOun3Diggsi05V@pendragon.ideasonboard.com/

-- 
Regards,

Laurent Pinchart

Re: [PATCH] media: uvcvideo: fix division by zero at stream start

[Johan Hovold]

On Fri, Dec 03, 2021 at 12:52:19PM +0200, Laurent Pinchart wrote:

> > I noticed that this one hasn't showed up in linux-next yet. Do you still
> > have it in your queue or do you want me to resend?
> 
> It should be in Mauro's queue now:
> 
> https://lore.kernel.org/all/YacOun3Diggsi05V@pendragon.ideasonboard.com/

Perfect, thanks!

Johan