media: hdpvr: Add device num check and handling

[ Upstream commit d4a6a9537bc32811486282206ecfb7c53754b74d ]

Add hdpvr device num check and error handling

We need to increment the device count atomically before we checkout a
device to make sure that we do not reach the max count, otherwise we get
out-of-bounds errors as reported by syzbot.

Reported-and-tested-by: syzbot+aac8d0d7205f112045d2@syzkaller.appspotmail.com
Signed-off-by: Luke Nowakowski-Krijger <lnowakow@eng.ucsd.edu>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/media/usb/hdpvr/hdpvr-core.c b/drivers/media/usb/hdpvr/hdpvr-core.c
index a20b60a..7b34108 100644 (file)
--- a/drivers/media/usb/hdpvr/hdpvr-core.c
+++ b/drivers/media/usb/hdpvr/hdpvr-core.c
@@ -278,6 +278,7 @@ static int hdpvr_probe(struct usb_interface *interface,
 #endif
        size_t buffer_size;
        int i;
+       int dev_num;
        int retval = -ENOMEM;
 
        /* allocate memory for our device state and initialize it */
@@ -382,8 +383,17 @@ static int hdpvr_probe(struct usb_interface *interface,
        }
 #endif
 
+       dev_num = atomic_inc_return(&dev_nr);
+       if (dev_num >= HDPVR_MAX) {
+               v4l2_err(&dev->v4l2_dev,
+                        "max device number reached, device register failed\n");
+               atomic_dec(&dev_nr);
+               retval = -ENODEV;
+               goto reg_fail;
+       }
+
        retval = hdpvr_register_videodev(dev, &interface->dev,
-                                   video_nr[atomic_inc_return(&dev_nr)]);
+                                   video_nr[dev_num]);
        if (retval < 0) {
                v4l2_err(&dev->v4l2_dev, "registering videodev failed\n");
                goto reg_fail;