Date: Wed,  6 Dec 2023 11:39:32 +0100
From: Johannes Berg <johannes@...solutions.net>
To: netdev@...r.kernel.org
Cc: Heiner Kallweit <hkallweit1@...il.com>,
	Johannes Berg <johannes.berg@...el.com>,
	Marc MERLIN <marc@...lins.org>,
	Przemek Kitszel <przemyslaw.kitszel@...el.com>
Subject: [PATCH net v3] net: ethtool: do runtime PM outside RTNL

From: Johannes Berg <johannes.berg@...el.com>

As reported by Marc MERLIN, at least one driver (igc) wants or
needs to acquire the RTNL inside suspend/resume ops, which can
be called from here in ethtool if runtime PM is enabled.

Allow this by doing runtime PM transitions without the RTNL
held. For the ioctl to have the same operations order, this
required reworking the code to separately check validity and
do the operation. For the netlink code, this now has to do
the runtime_pm_put a bit later.

Reported-by: Marc MERLIN <marc@...lins.org>
Fixes: f32a21376573 ("ethtool: runtime-resume netdev parent before ethtool ioctl ops")
Fixes: d43c65b05b84 ("ethtool: runtime-resume netdev parent in ethnl_ops_begin")
Closes: https://lore.kernel.org/r/20231202221402.GA11155@merlins.org
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@...el.com>
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
v2:
 - add tags
 - use netdev_get_by_name()/netdev_put() in ioctl path
v3:
 - drop if(dev) before netdev_put() [Przemek Kitszel]
 - add Reviewed-by tag
---
 net/ethtool/ioctl.c   | 71 ++++++++++++++++++++++++++-----------------
 net/ethtool/netlink.c | 32 ++++++++-----------
 2 files changed, 56 insertions(+), 47 deletions(-)

diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index a977f8903467..7c0e56985eb8 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2768,26 +2768,18 @@ static int ethtool_set_fecparam(struct net_device *dev, void __user *useraddr)
 /* The main entry point in this file.  Called from net/core/dev_ioctl.c */
 
 static int
-__dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr,
-	      u32 ethcmd, struct ethtool_devlink_compat *devlink_state)
+__dev_ethtool_check(struct net_device *dev, void __user *useraddr,
+		    u32 ethcmd, u32 *sub_cmd)
 {
-	struct net_device *dev;
-	u32 sub_cmd;
-	int rc;
-	netdev_features_t old_features;
-
-	dev = __dev_get_by_name(net, ifr->ifr_name);
-	if (!dev)
-		return -ENODEV;
-
 	if (ethcmd == ETHTOOL_PERQUEUE) {
-		if (copy_from_user(&sub_cmd, useraddr + sizeof(ethcmd), sizeof(sub_cmd)))
+		if (copy_from_user(sub_cmd, useraddr + sizeof(ethcmd), sizeof(*sub_cmd)))
 			return -EFAULT;
 	} else {
-		sub_cmd = ethcmd;
+		*sub_cmd = ethcmd;
 	}
+
 	/* Allow some commands to be done by anyone */
-	switch (sub_cmd) {
+	switch (*sub_cmd) {
 	case ETHTOOL_GSET:
 	case ETHTOOL_GDRVINFO:
 	case ETHTOOL_GMSGLVL:
@@ -2826,22 +2818,28 @@ __dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr,
 	case ETHTOOL_GFECPARAM:
 		break;
 	default:
-		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
+		if (!ns_capable(dev_net(dev)->user_ns, CAP_NET_ADMIN))
 			return -EPERM;
 	}
 
-	if (dev->dev.parent)
-		pm_runtime_get_sync(dev->dev.parent);
+	return 0;
+}
 
-	if (!netif_device_present(dev)) {
-		rc = -ENODEV;
-		goto out;
-	}
+static int
+__dev_ethtool_do(struct net_device *dev, struct ifreq *ifr,
+		 void __user *useraddr, u32 ethcmd, u32 sub_cmd,
+		 struct ethtool_devlink_compat *devlink_state)
+{
+	netdev_features_t old_features;
+	int rc;
+
+	if (!netif_device_present(dev))
+		return -ENODEV;
 
 	if (dev->ethtool_ops->begin) {
 		rc = dev->ethtool_ops->begin(dev);
 		if (rc < 0)
-			goto out;
+			return rc;
 	}
 	old_features = dev->features;
 
@@ -3052,7 +3050,7 @@ __dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr,
 		rc = ethtool_set_fecparam(dev, useraddr);
 		break;
 	default:
-		rc = -EOPNOTSUPP;
+		return -EOPNOTSUPP;
 	}
 
 	if (dev->ethtool_ops->complete)
@@ -3060,9 +3058,6 @@ __dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr,
 
 	if (old_features != dev->features)
 		netdev_features_change(dev);
-out:
-	if (dev->dev.parent)
-		pm_runtime_put(dev->dev.parent);
 
 	return rc;
 }
@@ -3070,7 +3065,9 @@ __dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr,
 int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 {
 	struct ethtool_devlink_compat *state;
-	u32 ethcmd;
+	struct net_device *dev = NULL;
+	netdevice_tracker dev_tracker;
+	u32 ethcmd, subcmd;
 	int rc;
 
 	if (copy_from_user(&ethcmd, useraddr, sizeof(ethcmd)))
@@ -3090,9 +3087,26 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 		break;
 	}
 
+	dev = netdev_get_by_name(net, ifr->ifr_name, &dev_tracker, GFP_KERNEL);
+	if (!dev) {
+		rc = -ENODEV;
+		goto exit_free;
+	}
+
+	rc = __dev_ethtool_check(dev, useraddr, ethcmd, &subcmd);
+	if (rc)
+		goto exit_free;
+
+	if (dev->dev.parent)
+		pm_runtime_get_sync(dev->dev.parent);
+
 	rtnl_lock();
-	rc = __dev_ethtool(net, ifr, useraddr, ethcmd, state);
+	rc = __dev_ethtool_do(dev, ifr, useraddr, ethcmd, subcmd, state);
 	rtnl_unlock();
+
+	if (dev->dev.parent)
+		pm_runtime_put(dev->dev.parent);
+
 	if (rc)
 		goto exit_free;
 
@@ -3115,6 +3129,7 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 	}
 
 exit_free:
+	netdev_put(dev, &dev_tracker);
 	if (state->devlink)
 		devlink_put(state->devlink);
 	kfree(state);
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index fe3553f60bf3..67e2dd893330 100644
--- a/net/ethtool/netlink.c
+++ b/net/ethtool/netlink.c
@@ -34,39 +34,23 @@ int ethnl_ops_begin(struct net_device *dev)
 {
 	int ret;
 
-	if (!dev)
-		return -ENODEV;
-
-	if (dev->dev.parent)
-		pm_runtime_get_sync(dev->dev.parent);
-
 	if (!netif_device_present(dev) ||
-	    dev->reg_state == NETREG_UNREGISTERING) {
-		ret = -ENODEV;
-		goto err;
-	}
+	    dev->reg_state == NETREG_UNREGISTERING)
+		return -ENODEV;
 
 	if (dev->ethtool_ops->begin) {
 		ret = dev->ethtool_ops->begin(dev);
 		if (ret)
-			goto err;
+			return ret;
 	}
 
 	return 0;
-err:
-	if (dev->dev.parent)
-		pm_runtime_put(dev->dev.parent);
-
-	return ret;
 }
 
 void ethnl_ops_complete(struct net_device *dev)
 {
 	if (dev->ethtool_ops->complete)
 		dev->ethtool_ops->complete(dev);
-
-	if (dev->dev.parent)
-		pm_runtime_put(dev->dev.parent);
 }
 
 /**
@@ -602,6 +586,14 @@ static int ethnl_default_set_doit(struct sk_buff *skb, struct genl_info *info)
 			goto out_dev;
 	}
 
+	if (!req_info.dev) {
+		ret = -ENODEV;
+		goto out_dev;
+	}
+
+	if (req_info.dev->dev.parent)
+		pm_runtime_get_sync(req_info.dev->dev.parent);
+
 	rtnl_lock();
 	ret = ethnl_ops_begin(req_info.dev);
 	if (ret < 0)
@@ -617,6 +609,8 @@ static int ethnl_default_set_doit(struct sk_buff *skb, struct genl_info *info)
 	ethnl_ops_complete(req_info.dev);
 out_rtnl:
 	rtnl_unlock();
+	if (req_info.dev->dev.parent)
+		pm_runtime_put(req_info.dev->dev.parent);
 out_dev:
 	ethnl_parse_header_dev_put(&req_info);
 	return ret;
-- 
2.43.0

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