Re: [PATCH v2] usb: Fix null-ptr-deref in qt2_process_read_urb()

[Johan Hovold <johan@kernel.org>]

On Sun, Jan 12, 2025 at 09:55:58AM +0000, Qasim Ijaz wrote:
> This patch addresses a null-ptr-deref in qt2_process_read_urb() due to
> an incorrect bounds check in the following:

Thanks for the fix. This looks correct, but your patch is whitespace
damaged (tabs replaced with spaces) and does not apply.

Can you please fix your mail setup and resend a v3? (Make sure to send
it to yourself first.)

When doing so, please use the common patch prefix for this driver:

	USB: serial: quatech2:

> ""

You can drop these (markup?) quotes.

>        if (newport > serial->num_ports) {
>                dev_err(&port->dev,
>                        "%s - port change to invalid port: %i\n",
>                        __func__, newport);
>                break;
>        }
> ""
> 
> The condition doesn't account for the valid range of the serial->port
> buffer, which is from 0 to serial->num_ports - 1. When newport is equal
> to serial->num_ports, the assignment of "port" in the
> following code is out-of-bounds and NULL:
> 
> ""
>        serial_priv->current_port = newport;
>        port = serial->port[serial_priv->current_port];
> 
> ""
> 
> The fix checks if newport is greater than or equal to serial->num_ports
> indicating it is out-of-bounds.
> 
> Reported-by: syzbot <syzbot+506479ebf12fe435d01a@syzkaller.appspotmail.com>
> Closes: https://syzkaller.appspot.com/bug?extid=506479ebf12fe435d01a
> Signed-off-by: Qasim Ijaz <qasdev00@gmail.com>

And please include a Fixes and CC stable tag:

	Fixes: f7a33e608d9a ("USB: serial: add quatech2 usb to serial driver")
	Cc: stable@vger.kernel.org	# 3.5

Johan