linux-kernel - Re: [PATCH] media: usb: technisat-usb2: fix buffer overflow

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Message-ID: <CAG_fn=VHpZW69TfK35aqL7o6CvgsPazL5raeW1QmWpu9ReYkhw@mail.gmail.com>
Date:   Tue, 2 Jul 2019 16:23:11 +0200
From:   Alexander Potapenko <glider@...gle.com>
To:     Phong Tran <tranmanphong@...il.com>
Cc:     syzbot+eaaaf38a95427be88f4b@...kaller.appspotmail.com,
        Andrey Konovalov <andreyknvl@...gle.com>,
        hans.verkuil@...co.com, mchehab@...nel.org,
        skhan@...uxfoundation.org, gregkh@...uxfoundation.org,
        Kees Cook <keescook@...omium.org>,
        LKML <linux-kernel@...r.kernel.org>, linux-media@...r.kernel.org,
        linux-usb@...r.kernel.org,
        syzkaller-bugs <syzkaller-bugs@...glegroups.com>,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: Re: [PATCH] media: usb: technisat-usb2: fix buffer overflow

On Tue, Jul 2, 2019 at 4:02 PM Phong Tran <tranmanphong@...il.com> wrote:
>
> The buffer will be overflow in case of the while loop can not break.
> Add the checking buffer condition in while loop for avoiding
> overlooping index.
>
> This issue was reported by syzbot
>
> Reported-by: syzbot+eaaaf38a95427be88f4b@...kaller.appspotmail.com
>
> Tested by:
> https://groups.google.com/d/msg/syzkaller-bugs/CySBCKuUOOs/0hKq1CdjCwAJ
>
> Signed-off-by: Phong Tran <tranmanphong@...il.com>
> ---
>  drivers/media/usb/dvb-usb/technisat-usb2.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/dvb-usb/technisat-usb2.c b/drivers/media/usb/dvb-usb/technisat-usb2.c
> index c659e18b358b..4e0b6185666a 100644
> --- a/drivers/media/usb/dvb-usb/technisat-usb2.c
> +++ b/drivers/media/usb/dvb-usb/technisat-usb2.c
> @@ -655,7 +655,7 @@ static int technisat_usb2_get_ir(struct dvb_usb_device *d)
>  #endif
>
>         ev.pulse = 0;
> -       while (1) {
> +       while (b != (buf + 63)) {
I think it won't hurt to either use ARRAY_SIZE here, or define some
magic constant for the buffer size in struct technisat_usb2_state.

>                 ev.pulse = !ev.pulse;
>                 ev.duration = (*b * FIRMWARE_CLOCK_DIVISOR * FIRMWARE_CLOCK_TICK) / 1000;
>                 ir_raw_event_store(d->rc_dev, &ev);
> --
> 2.11.0
>
> --
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-- 
Alexander Potapenko
Software Engineer

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