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From:   Alexander Potapenko <glider@google.com>
Date:   Tue, 2 Jul 2019 16:23:11 +0200
Message-ID: <CAG_fn=VHpZW69TfK35aqL7o6CvgsPazL5raeW1QmWpu9ReYkhw@mail.gmail.com>
Subject: Re: [PATCH] media: usb: technisat-usb2: fix buffer overflow
To:     Phong Tran <tranmanphong@gmail.com>
Cc:     syzbot+eaaaf38a95427be88f4b@syzkaller.appspotmail.com,
        Andrey Konovalov <andreyknvl@google.com>,
        hans.verkuil@cisco.com, mchehab@kernel.org,
        skhan@linuxfoundation.org, gregkh@linuxfoundation.org,
        Kees Cook <keescook@chromium.org>,
        LKML <linux-kernel@vger.kernel.org>, linux-media@vger.kernel.org,
        linux-usb@vger.kernel.org,
        syzkaller-bugs <syzkaller-bugs@googlegroups.com>,
        linux-kernel-mentees@lists.linuxfoundation.org
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On Tue, Jul 2, 2019 at 4:02 PM Phong Tran <tranmanphong@gmail.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@syzkaller.appspotmail.com
>
> Tested by:
> https://groups.google.com/d/msg/syzkaller-bugs/CySBCKuUOOs/0hKq1CdjCwAJ
>
> Signed-off-by: Phong Tran <tranmanphong@gmail.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/u=
sb/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_devic=
e *d)
>  #endif
>
>         ev.pulse =3D 0;
> -       while (1) {
> +       while (b !=3D (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 =3D !ev.pulse;
>                 ev.duration =3D (*b * FIRMWARE_CLOCK_DIVISOR * FIRMWARE_C=
LOCK_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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