netdev - Re: [PATCH net-next v3 5/6] devlink: hold a reference to the netdevice around ethtool compat

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Date:   Sun, 24 Feb 2019 12:00:03 +0100
From:   Jiri Pirko <jiri@...nulli.us>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     davem@...emloft.net, mkubecek@...e.cz, andrew@...n.ch,
        f.fainelli@...il.com, netdev@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: Re: [PATCH net-next v3 5/6] devlink: hold a reference to the
 netdevice around ethtool compat

Fri, Feb 22, 2019 at 11:07:56PM CET, jakub.kicinski@...ronome.com wrote:
>When ethtool is calling into devlink compat code make sure we have
>a reference on the netdevice on which the operation was invoked.
>
>v3: move the hold/lock logic into devlink_compat_* functions (Florian)
>
>Signed-off-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
>---
> net/core/devlink.c | 34 +++++++++++++++++++++++-----------
> net/core/ethtool.c | 13 ++-----------
> 2 files changed, 25 insertions(+), 22 deletions(-)
>
>diff --git a/net/core/devlink.c b/net/core/devlink.c
>index a13055160be0..78c6ea1870ca 100644
>--- a/net/core/devlink.c
>+++ b/net/core/devlink.c
>@@ -6430,27 +6430,39 @@ void devlink_compat_running_version(struct net_device *dev,
> {
> 	struct devlink *devlink;
> 
>+	dev_hold(dev);
>+	rtnl_unlock();

Ha, I got it now. You rely on dev_hold to make sure the
devlink instance does not dissappear. But until this patch, that is not
guaranteed (or I'm missing it).


>+
> 	devlink = netdev_to_devlink(dev);
>-	if (!devlink || !devlink->ops || !devlink->ops->info_get)
>-		return;
>+	if (devlink && devlink->ops && devlink->ops->info_get) {
>+		mutex_lock(&devlink->lock);
>+		__devlink_compat_running_version(devlink, buf, len);
>+		mutex_unlock(&devlink->lock);
>+	}
> 
>-	mutex_lock(&devlink->lock);
>-	__devlink_compat_running_version(devlink, buf, len);
>-	mutex_unlock(&devlink->lock);
>+	rtnl_lock();
>+	dev_put(dev);
> }
> 
> int devlink_compat_flash_update(struct net_device *dev, const char *file_name)
> {
> 	struct devlink *devlink;
>-	int ret;
>+	int ret = -EOPNOTSUPP;
>+
>+	dev_hold(dev);
>+	rtnl_unlock();
> 
> 	devlink = netdev_to_devlink(dev);
>-	if (!devlink || !devlink->ops || !devlink->ops->flash_update)
>-		return -EOPNOTSUPP;
>+	if (devlink && devlink->ops && devlink->ops->flash_update) {
>+		mutex_lock(&devlink->lock);
>+		ret = devlink->ops->flash_update(devlink, file_name,
>+						 NULL, NULL);
>+		mutex_unlock(&devlink->lock);
>+	}
>+
>+	rtnl_lock();
>+	dev_put(dev);
> 
>-	mutex_lock(&devlink->lock);
>-	ret = devlink->ops->flash_update(devlink, file_name, NULL, NULL);
>-	mutex_unlock(&devlink->lock);
> 	return ret;
> }
> 
>diff --git a/net/core/ethtool.c b/net/core/ethtool.c
>index 1320e8dce559..47558ffae423 100644
>--- a/net/core/ethtool.c
>+++ b/net/core/ethtool.c
>@@ -805,11 +805,9 @@ static noinline_for_stack int ethtool_get_drvinfo(struct net_device *dev,
> 	if (ops->get_eeprom_len)
> 		info.eedump_len = ops->get_eeprom_len(dev);
> 
>-	rtnl_unlock();
> 	if (!info.fw_version[0])
> 		devlink_compat_running_version(dev, info.fw_version,
> 					       sizeof(info.fw_version));
>-	rtnl_lock();
> 
> 	if (copy_to_user(useraddr, &info, sizeof(info)))
> 		return -EFAULT;
>@@ -2040,15 +2038,8 @@ static noinline_for_stack int ethtool_flash_device(struct net_device *dev,
> 		return -EFAULT;
> 	efl.data[ETHTOOL_FLASH_MAX_FILENAME - 1] = 0;
> 
>-	if (!dev->ethtool_ops->flash_device) {
>-		int ret;
>-
>-		rtnl_unlock();
>-		ret = devlink_compat_flash_update(dev, efl.data);
>-		rtnl_lock();
>-
>-		return ret;
>-	}
>+	if (!dev->ethtool_ops->flash_device)
>+		return devlink_compat_flash_update(dev, efl.data);
> 
> 	return dev->ethtool_ops->flash_device(dev, &efl);
> }
>-- 
>2.19.2
>