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

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Message-ID: <2b501d50-6777-a34f-7373-6648ed418794@microgate.com>
Date:   Tue, 15 Nov 2022 10:21:14 -0800
From:   Paul Fulghum <paulkf@...rogate.com>
To:     Zhengchao Shao <shaozhengchao@...wei.com>,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        jirislaby@...nel.org
Cc:     akpm@...ux-foundation.org, weiyongjun1@...wei.com,
        yuehaibing@...wei.com
Subject: [PATCH] tty: synclink_gt: unwind actions in error path of net device
 open

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@...wei.com>
Signed-off-by: Paul Fulghum <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;
  }