linux-kernel - [PATCH 4.4 21/30] media: uvcvideo: Allow entities with no pads

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Message-Id: <20210305120850.455189124@linuxfoundation.org>
Date:   Fri,  5 Mar 2021 13:22:50 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Ricardo Ribalda <ribalda@...omium.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Mauro Carvalho Chehab <mchehab+huawei@...nel.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.4 21/30] media: uvcvideo: Allow entities with no pads

From: Ricardo Ribalda <ribalda@...omium.org>

[ Upstream commit 7532dad6634031d083df7af606fac655b8d08b5c ]

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

Signed-off-by: Ricardo Ribalda <ribalda@...omium.org>
Signed-off-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@...nel.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/media/usb/uvc/uvc_driver.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/drivers/media/usb/uvc/uvc_driver.c b/drivers/media/usb/uvc/uvc_driver.c
index f353ab569b8e..def22b7fef9c 100644
--- a/drivers/media/usb/uvc/uvc_driver.c
+++ b/drivers/media/usb/uvc/uvc_driver.c
@@ -869,7 +869,10 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u8 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);
@@ -885,7 +888,7 @@ static struct uvc_entity *uvc_alloc_entity(u16 type, u8 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;
-- 
2.30.1