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From: Kees Cook <keescook@chromium.org>
To: Phong Tran <tranmanphong@gmail.com>
Cc: syzbot+eaaaf38a95427be88f4b@syzkaller.appspotmail.com,
	andreyknvl@google.com, hans.verkuil@cisco.com,
	mchehab@kernel.org, skhan@linuxfoundation.org,
	gregkh@linuxfoundation.org, linux-kernel@vger.kernel.org,
	linux-media@vger.kernel.org, linux-usb@vger.kernel.org,
	syzkaller-bugs@googlegroups.com,
	linux-kernel-mentees@lists.linuxfoundation.org
Subject: Re: [PATCH] media: usb: technisat-usb2: fix buffer overflow
Date: Tue, 2 Jul 2019 09:03:05 -0700	[thread overview]
Message-ID: <201907020858.66B63B24@keescook> (raw)
In-Reply-To: <20190702140211.28399-1-tranmanphong@gmail.com>

On Tue, Jul 02, 2019 at 09:02:11PM +0700, Phong Tran 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/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)) {

This matches the "62" from the earlier read -- instead of these literal
numbers, could you replace the "62"s with a named define for whatever
would make sense for this driver (maybe "IR_MAX_EVENTS"?), and then you
can make the above be something like:

	while (b <= buf + IR_MAX_EVENTS) {


>  		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
> 

-- 
Kees Cook

  parent reply	other threads:[~2019-07-03  0:58 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-14 20:06 KASAN: slab-out-of-bounds Read in technisat_usb2_rc_query syzbot
2019-07-02 14:02 ` [PATCH] media: usb: technisat-usb2: fix buffer overflow Phong Tran
2019-07-02 14:23   ` Alexander Potapenko
2019-07-02 16:03   ` Kees Cook [this message]
2019-07-03  2:14   ` [PATCH V2] " Phong Tran
2019-07-03  2:26     ` Kees Cook
2019-07-03 14:52 ` [PATCH] media: technisat-usb2: break out of loop at end of buffer Sean Young
2019-07-03 16:54   ` Kees Cook

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