linux-kernel - Re: [PATCH] tty: synclink_gt: unwind actions in error path of net device open

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Date:   Tue, 15 Nov 2022 18:10:27 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Paul Fulghum <paulkf@...rogate.com>
Cc:     Zhengchao Shao <shaozhengchao@...wei.com>,
        "linux-kernel@...r.kernel.org Mailing List" 
        <linux-kernel@...r.kernel.org>, Jiri Slaby <jirislaby@...nel.org>,
        akpm@...ux-foundation.org, weiyongjun1@...wei.com,
        yuehaibing@...wei.com
Subject: Re: [PATCH] tty: synclink_gt: unwind actions in error path of net
 device open

On Tue, Nov 15, 2022 at 08:25:13AM -0800, Paul Fulghum wrote:
> Zhengchao Shao <shaozhengchao@...wei.com <mailto:shaozhengchao@...wei.com>> identified by inspection bugs in the error path of hdlcdev_open() in synclink_gt.c
> 
> The function did not fully unwind actions in the error path. The use of try_module_get()/module_put() is unnecessary, potentially hazardous and is removed. The synclink_gt driver is already pinned any point the net device is registered, a requirement for calling this entry point.
> 
> The call hdlc_open() to init the generic HDLC layer is moved to after driver level init/checks and proper rollback of previous actions is added. This is a more sensible ordering as the most common error paths are at the driver level and the driver level rollbacks require less processing than hdlc_open()/hdlc_close().
> 
> This has been tested with supported hardware.
> 
> Signed-off-by:Paul Fulghum <paulkf@...rogate.com <mailto:paulkf@...rogate.com>>
> 
> 
> diff --git a/drivers/tty/synclink_gt.c b/drivers/tty/synclink_gt.c
> index 25e9befdda3a..72b76cdde534 100644
> --- a/drivers/tty/synclink_gt.c
> +++ b/drivers/tty/synclink_gt.c
> @@ -1433,16 +1433,8 @@ static int hdlcdev_open(struct net_device *dev)
>  	int rc;
>  	unsigned long flags;
>  
> -	if (!try_module_get(THIS_MODULE))
> -		return -EBUSY;
> -
>  	DBGINFO(("%s hdlcdev_open\n", dev->name));
>  
> -	/* generic HDLC layer open processing */
> -	rc = hdlc_open(dev);
> -	if (rc)
> -		return rc;
> -
>  	/* arbitrate between network and tty opens */
>  	spin_lock_irqsave(&info->netlock, flags);
>  	if (info->port.count != 0 || info->netcount != 0) {
> @@ -1461,6 +1453,16 @@ static int hdlcdev_open(struct net_device *dev)
>  		return rc;
>  	}
>  
> +	/* generic HDLC layer open processing */
> +	rc = hdlc_open(dev);
> +	if (rc) {
> +		shutdown(info);
> +		spin_lock_irqsave(&info->netlock, flags);
> +		info->netcount = 0;
> +		spin_unlock_irqrestore(&info->netlock, flags);
> +		return rc;
> +	}
> +
>  	/* assert RTS and DTR, apply hardware settings */
>  	info->signals |= SerialSignal_RTS | SerialSignal_DTR;
>  	program_hw(info);
> @@ -1506,7 +1508,6 @@ static int hdlcdev_close(struct net_device *dev)
>  	info->netcount=0;
>  	spin_unlock_irqrestore(&info->netlock, flags);
>  
> -	module_put(THIS_MODULE);
>  	return 0;
>  }
>  
> 

Hi,

This is the friendly patch-bot of Greg Kroah-Hartman.  You have sent him
a patch that has triggered this response.  He used to manually respond
to these common problems, but in order to save his sanity (he kept
writing the same thing over and over, yet to different people), I was
created.  Hopefully you will not take offence and will fix the problem
in your patch and resubmit it so that it can be accepted into the Linux
kernel tree.

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