[PATCH] Fix an OOB access bug in technisat_usb2_get_ir

[Hui Peng]

In the while loop of technisat_usb2_get_ir, it scans through
a fix-sized buffer read from the device side, the termination
condition of the loop is `*b == 0xff`. If no `0xff` byte is read
from the device side, OOB access happens.

This patch fixes the bug by adding an upper bound in the while loop.

Reported-by: Hui Peng <benqu...@gmail.com>
Reported-by: Mathias Payer <mathias.pa...@nebelwelt.net>
Signed-off-by: Hui Peng <benqu...@gmail.com>
---
 drivers/media/usb/dvb-usb/technisat-usb2.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/media/usb/dvb-usb/technisat-usb2.c 
b/drivers/media/usb/dvb-usb/technisat-usb2.c
index c659e18b358b..181f5f97af45 100644
--- a/drivers/media/usb/dvb-usb/technisat-usb2.c
+++ b/drivers/media/usb/dvb-usb/technisat-usb2.c
@@ -612,6 +612,7 @@ static int technisat_usb2_get_ir(struct dvb_usb_device *d)
        u8 *b;
        int ret;
        struct ir_raw_event ev;
+       int i = 0;
 
        buf[0] = GET_IR_DATA_VENDOR_REQUEST;
        buf[1] = 0x08;
@@ -656,11 +657,15 @@ static int technisat_usb2_get_ir(struct dvb_usb_device *d)
 
        ev.pulse = 0;
        while (1) {
+               // only `ret` bytes are read from the device side
+               if (i >= ret)
+                       break;
                ev.pulse = !ev.pulse;
                ev.duration = (*b * FIRMWARE_CLOCK_DIVISOR * 
FIRMWARE_CLOCK_TICK) / 1000;
                ir_raw_event_store(d->rc_dev, &ev);
 
                b++;
+               i++;
                if (*b == 0xff) {
                        ev.pulse = 0;
                        ev.duration = 888888*2;
-- 
2.23.0