media: imon: fix access to invalid resource for the second interface

imon driver probes two USB interfaces, and at the probe of the second
interface, the driver assumes blindly that the first interface got
bound with the same imon driver.  It's usually true, but it's still
possible that the first interface is bound with another driver via a
malformed descriptor.  Then it may lead to a memory corruption, as
spotted by syzkaller; imon driver accesses the data from drvdata as
struct imon_context object although it's a completely different one
that was assigned by another driver.

This patch adds a sanity check -- whether the first interface is
really bound with the imon driver or not -- for avoiding the problem
above at the probe time.

Reported-by: [email protected]
Closes: https://lore.kernel.org/all/[email protected]/
Tested-by: Ricardo B. Marliere <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Takashi Iwai <[email protected]>
Signed-off-by: Sean Young <[email protected]>
Signed-off-by: Hans Verkuil <[email protected]>

drivers/media/rc/imon.c

@@ -2427,6 +2427,12 @@ static int imon_probe(struct usb_interface *interface,
 		goto fail;
 	}
 
+	if (first_if->dev.driver != interface->dev.driver) {
+		dev_err(&interface->dev, "inconsistent driver matching\n");
+		ret = -EINVAL;
+		goto fail;
+	}
+
 	if (ifnum == 0) {
 		ictx = imon_init_intf0(interface, id);
 		if (!ictx) {