[PATCH AUTOSEL 5.2 019/185] media: hdpvr: Add device num check and handling

Sasha Levin
2019-09-22T19:29:13Z

From: Luke Nowakowski-Krijger <lnowakow@eng.ucsd.edu>

[ 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>
---
drivers/media/usb/hdpvr/hdpvr-core.c | 12 +++++++++++-
1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/hdpvr/hdpvr-core.c b/drivers/media/usb/hdpvr/hdpvr-core.c
index 9b9d894d29bcb..a0905c81d2cb2 100644
--- a/drivers/media/usb/hdpvr/hdpvr-core.c
+++ b/drivers/media/usb/hdpvr/hdpvr-core.c
@@ -271,6 +271,7 @@ 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 */
@@ -368,8 +369,17 @@ 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;
--
2.20.1