media: uvcvideo: Allow entities with no pads

Avoid an underflow while calculating the number of inputs for entities
with zero pads.

Signed-off-by: Ricardo Ribalda <ribalda@chromium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index dd2e499..a9b94fb 100644 (file)
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -1033,7 +1033,10 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
        unsigned int i;
 
        extra_size = roundup(extra_size, sizeof(*entity->pads));
-       num_inputs = (type & UVC_TERM_OUTPUT) ? num_pads : num_pads - 1;
+       if (num_pads)
+               num_inputs = type & UVC_TERM_OUTPUT ? num_pads : num_pads - 1;
+       else
+               num_inputs = 0;
        size = sizeof(*entity) + extra_size + sizeof(*entity->pads) * num_pads
             + num_inputs;
        entity = kzalloc(size, GFP_KERNEL);
@@ -1065,7 +1068,7 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u16 id,
 
        for (i = 0; i < num_inputs; ++i)
                entity->pads[i].flags = MEDIA_PAD_FL_SINK;
-       if (!UVC_ENTITY_IS_OTERM(entity))
+       if (!UVC_ENTITY_IS_OTERM(entity) && num_pads)
                entity->pads[num_pads-1].flags = MEDIA_PAD_FL_SOURCE;
 
        entity->bNrInPins = num_inputs;