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Date: Mon,  4 Dec 2023 20:07:06 +0100
From: Johannes Berg <johannes@...solutions.net>
To: netdev@...r.kernel.org
Cc: Marc MERLIN <marc@...lins.org>,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Tony Nguyen <anthony.l.nguyen@...el.com>,
	intel-wired-lan@...ts.osuosl.org,
	Heiner Kallweit <hkallweit1@...il.com>,
	Johannes Berg <johannes.berg@...el.com>
Subject: [RFC PATCH] net: ethtool: do runtime PM outside RTNL

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

As reported by Marc MERLIN in [1], at least one driver (igc)
wants/needs to acquire the RTNL inside suspend/resume ops,
which can be called from here in ethtool if runtime PM is
enabled.

[1] https://lore.kernel.org/r/20231202221402.GA11155@merlins.org

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.

Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 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 0b0ce4f81c01..ae7e165dc471 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -2765,26 +2765,18 @@ 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:
@@ -2823,22 +2815,28 @@ __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;
 
@@ -3049,7 +3047,7 @@ __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)
@@ -3057,9 +3055,6 @@ __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;
 }
@@ -3067,7 +3062,8 @@ __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;
+	u32 ethcmd, subcmd;
 	int rc;
 
 	if (copy_from_user(&ethcmd, useraddr, sizeof(ethcmd)))
@@ -3087,9 +3083,26 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 		break;
 	}
 
+	dev = dev_get_by_name(net, ifr->ifr_name);
+	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;
 
@@ -3112,6 +3125,8 @@ int dev_ethtool(struct net *net, struct ifreq *ifr, void __user *useraddr)
 	}
 
 exit_free:
+	if (dev)
+		dev_put(dev);
 	if (state->devlink)
 		devlink_put(state->devlink);
 	kfree(state);
diff --git a/net/ethtool/netlink.c b/net/ethtool/netlink.c
index fe3553f60bf3..ee9ccf64688d 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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