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SubjectRe: [PATCH] media: technisat-usb2: break out of loop at end of buffer
On Wed, Jul 03, 2019 at 03:52:39PM +0100, Sean Young wrote:
> 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>

Both you and Phong Tran appear to be working on fixing this. At a
glance, this patch appears to be more complete in that it makes the code
flow more sane too.

Reviewed-by: Kees Cook <keescook@chromium.org>

-Kees

> ---
> drivers/media/usb/dvb-usb/technisat-usb2.c | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/media/usb/dvb-usb/technisat-usb2.c b/drivers/media/usb/dvb-usb/technisat-usb2.c
> index c659e18b358b..676d233d46d5 100644
> --- a/drivers/media/usb/dvb-usb/technisat-usb2.c
> +++ b/drivers/media/usb/dvb-usb/technisat-usb2.c
> @@ -608,10 +608,9 @@ static int technisat_usb2_frontend_attach(struct dvb_usb_adapter *a)
> static int technisat_usb2_get_ir(struct dvb_usb_device *d)
> {
> struct technisat_usb2_state *state = d->priv;
> - u8 *buf = state->buf;
> - u8 *b;
> - int ret;
> struct ir_raw_event ev;
> + u8 *buf = state->buf;
> + int i, ret;
>
> buf[0] = GET_IR_DATA_VENDOR_REQUEST;
> buf[1] = 0x08;
> @@ -647,26 +646,25 @@ static int technisat_usb2_get_ir(struct dvb_usb_device *d)
> 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(state->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);
> --
> 2.21.0
>

--
Kees Cook

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