linux-kernel - Re: [PATCH v2] Bluetooth: bfusb: Fix buffer over-read in rx processing loop

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Message-ID: <77bde79f-2080-4e40-a013-52b480c0928c@molgen.mpg.de>
Date: Wed, 8 Oct 2025 05:51:52 +0200
From: Paul Menzel <pmenzel@...gen.mpg.de>
To: Seungjin Bae <eeodqql09@...il.com>
Cc: Marcel Holtmann <marcel@...tmann.org>,
 Kyungtae Kim <Kyungtae.Kim@...tmouth.edu>,
 Luiz Augusto von Dentz <luiz.dentz@...il.com>, linux-kernel@...r.kernel.org,
 linux-bluetooth@...r.kernel.org, stable@...r.kernel.org
Subject: Re: [PATCH v2] Bluetooth: bfusb: Fix buffer over-read in rx
 processing loop

Dear Seungjin,


Thank you for the patch.

Am 08.10.25 um 03:56 schrieb pip-izony:
> From: Seungjin Bae <eeodqql09@...il.com>
> 
> The bfusb_rx_complete() function parses incoming URB data in while loop.

… in *a* while loop.

> The logic does not sufficiently validate the remaining buffer size(count)
> accross loop iterations, which can lead to a buffer over-read.

across

> For example, with 4-bytes remaining buffer, if the first iteration takes
> the `hdr & 0x4000` branch, 2-bytes are consumed. On the next iteration,
> only 2-bytes remain, but the else branch is trying to access the third
> byte(buf[2]). This causes an out-of-bounds read and a potential kernel panic.

Please re-flow for 75 characters per line.

> This patch fixes the vulnerability by adding checks to ensure enough
> data remains in the buffer before it is accessed.
> 
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Seungjin Bae <eeodqql09@...il.com>
> ---
>   v1 -> v2: Fixing the error function name
>   
>   drivers/bluetooth/bfusb.c | 4 ++++
>   1 file changed, 4 insertions(+)
> 
> diff --git a/drivers/bluetooth/bfusb.c b/drivers/bluetooth/bfusb.c
> index 8df310983bf6..45f4ec5b6860 100644
> --- a/drivers/bluetooth/bfusb.c
> +++ b/drivers/bluetooth/bfusb.c
> @@ -360,6 +360,10 @@ static void bfusb_rx_complete(struct urb *urb)
>   			count -= 2;
>   			buf   += 2;
>   		} else {
> +            if (count < 3) {
> +                bt_dev_err(data->hdev, "block header is too short");

Please print count and 3.

> +                break;
> +            }

Please use tabs for alignment. `scripts/checkpatch.pl` should have 
warned about this.

>   			len = (buf[2] == 0) ? 256 : buf[2];
>   			count -= 3;
>   			buf   += 3;


Kind regards,

Paul