linux-kernel - Re: [PATCH] usb: gadget: u_serial: Add null pointer check in gserial

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Message-ID: <Y+O3vBbBh4ZwSBWT@kroah.com>
Date:   Wed, 8 Feb 2023 15:54:52 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Prashanth K <quic_prashk@...cinc.com>
Cc:     Christophe JAILLET <christophe.jaillet@...adoo.fr>,
        Xiu Jianfeng <xiujianfeng@...wei.com>,
        Pratham Pratap <quic_ppratap@...cinc.com>,
        Jack Pham <quic_jackp@...cinc.com>, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb: gadget: u_serial: Add null pointer check in
 gserial_resume

On Wed, Feb 08, 2023 at 07:24:47PM +0530, Prashanth K wrote:
> Consider a case where gserial_disconnect has already cleared
> gser->ioport. And if a wakeup interrupt triggers afterwards,
> gserial_resume gets called, which will lead to accessing of
> gserial->port and thus causing null pointer dereference.Add
> a null pointer check to prevent this.
> 
> Fixes: aba3a8d01d62 (" usb: gadget: u_serial: add suspend resume callbacks")

Nit, and our tools will complain, no " " before the "usb:" string here,
right?



> Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
> ---
>  drivers/usb/gadget/function/u_serial.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/usb/gadget/function/u_serial.c b/drivers/usb/gadget/function/u_serial.c
> index 840626e..98be2b8 100644
> --- a/drivers/usb/gadget/function/u_serial.c
> +++ b/drivers/usb/gadget/function/u_serial.c
> @@ -1428,6 +1428,9 @@ void gserial_resume(struct gserial *gser)
>  	struct gs_port *port = gser->ioport;
>  	unsigned long	flags;
>  
> +	if (!port)
> +		return;
> +

What prevents port from going to NULL right after this check?

thanks,

greg k-h