[PATCH AUTOSEL 4.9 15/20] media: dvb_net: avoid speculation from net slot

[Sasha Levin <sashal@kernel.org>]

From: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

[ Upstream commit abc0226df64dc137b48b911c1fe4319aec5891bb ]

The risk of especulation is actually almost-non-existing here,
as there are very few users of TCP/IP using the DVB stack,
as, this is mainly used with DVB-S/S2 cards, and only by people
that receives TCP/IP from satellite connections, which limits
a lot the number of users of such feature(*).

(*) In thesis, DVB-C cards could also benefit from it, but I'm
yet to see a hardware that supports it.

Yet, fixing it is trivial.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/media/dvb-core/dvb_net.c | 25 +++++++++++++++++++------
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/drivers/media/dvb-core/dvb_net.c b/drivers/media/dvb-core/dvb_net.c
index 9914f69a4a02..f133489af9b9 100644
--- a/drivers/media/dvb-core/dvb_net.c
+++ b/drivers/media/dvb-core/dvb_net.c
@@ -57,6 +57,7 @@
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/netdevice.h>
+#include <linux/nospec.h>
 #include <linux/etherdevice.h>
 #include <linux/dvb/net.h>
 #include <linux/uio.h>
@@ -1350,14 +1351,20 @@ static int dvb_net_do_ioctl(struct file *file,
 		struct net_device *netdev;
 		struct dvb_net_priv *priv_data;
 		struct dvb_net_if *dvbnetif = parg;
+		int if_num = dvbnetif->if_num;
 
-		if (dvbnetif->if_num >= DVB_NET_DEVICES_MAX ||
-		    !dvbnet->state[dvbnetif->if_num]) {
+		if (if_num >= DVB_NET_DEVICES_MAX) {
 			ret = -EINVAL;
 			goto ioctl_error;
 		}
+		if_num = array_index_nospec(if_num, DVB_NET_DEVICES_MAX);
 
-		netdev = dvbnet->device[dvbnetif->if_num];
+		if (!dvbnet->state[if_num]) {
+			ret = -EINVAL;
+			goto ioctl_error;
+		}
+
+		netdev = dvbnet->device[if_num];
 
 		priv_data = netdev_priv(netdev);
 		dvbnetif->pid=priv_data->pid;
@@ -1410,14 +1417,20 @@ static int dvb_net_do_ioctl(struct file *file,
 		struct net_device *netdev;
 		struct dvb_net_priv *priv_data;
 		struct __dvb_net_if_old *dvbnetif = parg;
+		int if_num = dvbnetif->if_num;
+
+		if (if_num >= DVB_NET_DEVICES_MAX) {
+			ret = -EINVAL;
+			goto ioctl_error;
+		}
+		if_num = array_index_nospec(if_num, DVB_NET_DEVICES_MAX);
 
-		if (dvbnetif->if_num >= DVB_NET_DEVICES_MAX ||
-		    !dvbnet->state[dvbnetif->if_num]) {
+		if (!dvbnet->state[if_num]) {
 			ret = -EINVAL;
 			goto ioctl_error;
 		}
 
-		netdev = dvbnet->device[dvbnetif->if_num];
+		netdev = dvbnet->device[if_num];
 
 		priv_data = netdev_priv(netdev);
 		dvbnetif->pid=priv_data->pid;
-- 
2.30.2