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

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Nov 15, 2022 at 10:21:14AM -0800, Paul Fulghum wrote:
> hdlcdev_open() in synclink_gt.c 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.
> 
> Suggested-by: Zhengchao Shao <shaozhengchao@huawei.com>
> Signed-off-by: Paul Fulghum <paulkf@microgate.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;
>  }
> 


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