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From: Kees Cook <keescook@chromium.org>
To: Phong Tran <tranmanphong@gmail.com>
Cc: andreyknvl@google.com, gregkh@linuxfoundation.org,
	hans.verkuil@cisco.com,
	linux-kernel-mentees@lists.linuxfoundation.org,
	linux-kernel@vger.kernel.org, linux-media@vger.kernel.org,
	linux-usb@vger.kernel.org, mchehab@kernel.org,
	skhan@linuxfoundation.org,
	syzbot+eaaaf38a95427be88f4b@syzkaller.appspotmail.com,
	syzkaller-bugs@googlegroups.com, glider@google.com
Subject: Re: [PATCH V2] media: usb: technisat-usb2: fix buffer overflow
Date: Tue, 2 Jul 2019 19:26:32 -0700	[thread overview]
Message-ID: <201907021925.1F24D6ADA3@keescook> (raw)
In-Reply-To: <20190703021444.19954-1-tranmanphong@gmail.com>

On Wed, Jul 03, 2019 at 09:14:44AM +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/t3PvVheSAAAJ
> 

Avoid these blank lines please. (More below...)

> Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> ---
> Change Log:
>  * V2: add IR_MAX_BUFFER_INDEX and adjust the while loop condition as comments
> ---
>  drivers/media/usb/dvb-usb/technisat-usb2.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/dvb-usb/technisat-usb2.c b/drivers/media/usb/dvb-usb/technisat-usb2.c
> index c659e18b358b..cdabff97c1ea 100644
> --- a/drivers/media/usb/dvb-usb/technisat-usb2.c
> +++ b/drivers/media/usb/dvb-usb/technisat-usb2.c
> @@ -49,6 +49,7 @@ MODULE_PARM_DESC(disable_led_control,
>  		"disable LED control of the device (default: 0 - LED control is active).");
>  
>  /* device private data */
> +#define IR_MAX_BUFFER_INDEX	63

How does this map to the literal "62" used before the loop you're
fixing?

Otherwise, it's looking good; thanks!

-Kees

>  struct technisat_usb2_state {
>  	struct dvb_usb_device *dev;
>  	struct delayed_work green_led_work;
> @@ -56,7 +57,7 @@ struct technisat_usb2_state {
>  
>  	u16 last_scan_code;
>  
> -	u8 buf[64];
> +	u8 buf[IR_MAX_BUFFER_INDEX + 1];
>  };
>  
>  /* debug print helpers */
> @@ -655,7 +656,7 @@ static int technisat_usb2_get_ir(struct dvb_usb_device *d)
>  #endif
>  
>  	ev.pulse = 0;
> -	while (1) {
> +	while (b <= (buf + IR_MAX_BUFFER_INDEX)) {
>  		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

  reply	other threads:[~2019-07-03  2:26 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
2019-07-03  2:14   ` [PATCH V2] " Phong Tran
2019-07-03  2:26     ` Kees Cook [this message]
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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