[PATCH 1/6] ALSA: aloop: Check card index validity at probe

aloop driver blindly trusts that the given devptr->id value is within
the proper card index range at probe.  It's OK for the devices the
driver itself creates at the module probe time, but if the device is
bound manually via sysfs interface, this could be -1 as "none", and
this leads to OOB access for index[] and other parameters.

Add a sanity check for the card index and warn/correct it if it's a
value out of the range.

Cc: <[email protected]>
Signed-off-by: Takashi Iwai <[email protected]>
---
 sound/drivers/aloop.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index d520d83c2577..92ef821ddbeb 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -1914,6 +1914,12 @@ static int loopback_probe(struct platform_device *devptr)
 	int dev = devptr->id;
 	int err;
 
+	if (dev < 0 || dev >= SNDRV_CARDS) {
+		dev_warn(&devptr->dev,
+			 "Invalid card index %d, using default 0\n", dev);
+		dev = 0;
+	}
+
 	err = snd_devm_card_new(&devptr->dev, index[dev], id[dev], THIS_MODULE,
 				sizeof(struct loopback), &card);
 	if (err < 0)
-- 
2.55.0