media: technisat-usb2: break out of loop at end of buffer

commit 0c4df39e504bf925ab666132ac3c98d6cbbe380b upstream.

Ensure we do not access the buffer beyond the end if no 0xff byte
is encountered.

Reported-by: syzbot+eaaaf38a95427be88f4b@syzkaller.appspotmail.com
Signed-off-by: Sean Young <sean@mess.org>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
[bwh: Backported to 3.16: technisat_usb2_get_ir() still uses a stack
 buffer, which is not worth fixing on this branch]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/media/usb/dvb-usb/technisat-usb2.c b/drivers/media/usb/dvb-usb/technisat-usb2.c
index d947e0379008b9aa6bc857272f3faedb45fb46a2..1e1123be9bcc6c4622ff19665231ba655f3d116d 100644 (file)
--- a/drivers/media/usb/dvb-usb/technisat-usb2.c
+++ b/drivers/media/usb/dvb-usb/technisat-usb2.c
@@ -591,9 +591,9 @@ static int technisat_usb2_frontend_attach(struct dvb_usb_adapter *a)
 
 static int technisat_usb2_get_ir(struct dvb_usb_device *d)
 {
-       u8 buf[62], *b;
-       int ret;
        struct ir_raw_event ev;
+       u8 buf[62];
+       int i, ret;
 
        buf[0] = GET_IR_DATA_VENDOR_REQUEST;
        buf[1] = 0x08;
@@ -629,26 +629,25 @@ unlock:
                return 0; /* no key pressed */
 
        /* decoding */
-       b = buf+1;
 
 #if 0
        deb_rc("RC: %d ", ret);
-       debug_dump(b, ret, deb_rc);
+       debug_dump(buf + 1, ret, deb_rc);
 #endif
 
        ev.pulse = 0;
-       while (1) {
-               ev.pulse = !ev.pulse;
-               ev.duration = (*b * FIRMWARE_CLOCK_DIVISOR * FIRMWARE_CLOCK_TICK) / 1000;
-               ir_raw_event_store(d->rc_dev, &ev);
-
-               b++;
-               if (*b == 0xff) {
+       for (i = 1; i < ARRAY_SIZE(buf); i++) {
+               if (buf[i] == 0xff) {
                        ev.pulse = 0;
                        ev.duration = 888888*2;
                        ir_raw_event_store(d->rc_dev, &ev);
                        break;
                }
+
+               ev.pulse = !ev.pulse;
+               ev.duration = (buf[i] * FIRMWARE_CLOCK_DIVISOR *
+                              FIRMWARE_CLOCK_TICK) / 1000;
+               ir_raw_event_store(d->rc_dev, &ev);
        }
 
        ir_raw_event_handle(d->rc_dev);