Re: [PATCH] driver: usb: nullify dangling pointer in cdc_ncm_free

[Oliver Neukum <oneukum@suse.com>]

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So I am afraid I have to ask again, whether anybody sees a fundamental
issue with the new version attached patch, as opposed to it not being an
elegant
solution?

I corrected the stuff Johan found and split the method in the asix driver.

I do not understand smsc95xx well, so I left it in the current state.


    Regards
        Oliver

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From 5953b3b12dd6cdd8d0bdb0119ee627d62219ab1e Mon Sep 17 00:00:00 2001
From: Oliver Neukum <oneukum@suse.com>
Date: Thu, 10 Mar 2022 13:18:38 +0100
Subject: [PATCH] usbnet: split unbind callback

Some devices need to be informed of a disconnect before
the generic layer is informed, others need their notification
later to avoid race conditions. Hence we provide two callbacks.

Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/net/usb/asix_devices.c | 13 +++++++++++--
 drivers/net/usb/smsc95xx.c     |  4 ++--
 drivers/net/usb/usbnet.c       | 10 +++++++---
 include/linux/usb/usbnet.h     |  3 +++
 4 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/drivers/net/usb/asix_devices.c b/drivers/net/usb/asix_devices.c
index 38e47a93fb83..cde4d234b975 100644
--- a/drivers/net/usb/asix_devices.c
+++ b/drivers/net/usb/asix_devices.c
@@ -804,12 +804,18 @@ static int ax88772_stop(struct usbnet *dev)
 	return 0;
 }
 
-static void ax88772_unbind(struct usbnet *dev, struct usb_interface *intf)
+static void ax88772_disable(struct usbnet *dev, struct usb_interface *intf)
 {
 	struct asix_common_private *priv = dev->driver_priv;
 
 	phy_disconnect(priv->phydev);
-	asix_rx_fixup_common_free(dev->driver_priv);
+}
+
+static void ax88772_unbind(struct usbnet *dev, struct usb_interface *intf)
+{
+	struct asix_common_private *priv = dev->driver_priv;
+
+	asix_rx_fixup_common_free(priv);
 }
 
 static void ax88178_unbind(struct usbnet *dev, struct usb_interface *intf)
@@ -1211,6 +1217,7 @@ static const struct driver_info ax88772_info = {
 	.description = "ASIX AX88772 USB 2.0 Ethernet",
 	.bind = ax88772_bind,
 	.unbind = ax88772_unbind,
+	.disable = ax88772_disable,
 	.status = asix_status,
 	.reset = ax88772_reset,
 	.stop = ax88772_stop,
@@ -1223,6 +1230,7 @@ static const struct driver_info ax88772b_info = {
 	.description = "ASIX AX88772B USB 2.0 Ethernet",
 	.bind = ax88772_bind,
 	.unbind = ax88772_unbind,
+	.disable = ax88772_disable,
 	.status = asix_status,
 	.reset = ax88772_reset,
 	.stop = ax88772_stop,
@@ -1259,6 +1267,7 @@ static const struct driver_info hg20f9_info = {
 	.description = "HG20F9 USB 2.0 Ethernet",
 	.bind = ax88772_bind,
 	.unbind = ax88772_unbind,
+	.disable = ax88772_disable,
 	.status = asix_status,
 	.reset = ax88772_reset,
 	.flags = FLAG_ETHER | FLAG_FRAMING_AX | FLAG_LINK_INTR |
diff --git a/drivers/net/usb/smsc95xx.c b/drivers/net/usb/smsc95xx.c
index 4ef61f6b85df..20ce88373809 100644
--- a/drivers/net/usb/smsc95xx.c
+++ b/drivers/net/usb/smsc95xx.c
@@ -1223,7 +1223,7 @@ static int smsc95xx_bind(struct usbnet *dev, struct usb_interface *intf)
 	return ret;
 }
 
-static void smsc95xx_unbind(struct usbnet *dev, struct usb_interface *intf)
+static void smsc95xx_disable(struct usbnet *dev, struct usb_interface *intf)
 {
 	struct smsc95xx_priv *pdata = dev->driver_priv;
 
@@ -1997,7 +1997,7 @@ static int smsc95xx_manage_power(struct usbnet *dev, int on)
 static const struct driver_info smsc95xx_info = {
 	.description	= "smsc95xx USB 2.0 Ethernet",
 	.bind		= smsc95xx_bind,
-	.unbind		= smsc95xx_unbind,
+	.disable	= smsc95xx_disable,
 	.link_reset	= smsc95xx_link_reset,
 	.reset		= smsc95xx_reset,
 	.check_connect	= smsc95xx_start_phy,
diff --git a/drivers/net/usb/usbnet.c b/drivers/net/usb/usbnet.c
index b1f93810a6f3..5f3851e61573 100644
--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -1641,17 +1641,21 @@ void usbnet_disconnect (struct usb_interface *intf)
 		   xdev->bus->bus_name, xdev->devpath,
 		   dev->driver_info->description);
 
-	if (dev->driver_info->unbind)
-		dev->driver_info->unbind(dev, intf);
+	if (dev->driver_info->disable)
+		dev->driver_info->disable(dev, intf);
 
 	net = dev->net;
 	unregister_netdev (net);
 
+	usb_kill_urb(dev->interrupt);
+
 	cancel_work_sync(&dev->kevent);
 
 	usb_scuttle_anchored_urbs(&dev->deferred);
 
-	usb_kill_urb(dev->interrupt);
+	if (dev->driver_info->unbind)
+		dev->driver_info->unbind (dev, intf);
+
 	usb_free_urb(dev->interrupt);
 	kfree(dev->padding_pkt);
 
diff --git a/include/linux/usb/usbnet.h b/include/linux/usb/usbnet.h
index 1b4d72d5e891..dd4a1104e332 100644
--- a/include/linux/usb/usbnet.h
+++ b/include/linux/usb/usbnet.h
@@ -129,6 +129,9 @@ struct driver_info {
 	/* cleanup device ... can sleep, but can't fail */
 	void	(*unbind)(struct usbnet *, struct usb_interface *);
 
+	/* disable device ... can sleep, but can't fail */
+	void	(*disable)(struct usbnet *, struct usb_interface *);
+
 	/* reset device ... can sleep */
 	int	(*reset)(struct usbnet *);
 
-- 
2.34.1