[PATCH net-next v2 04/11] net: ethtool: add netif_get_link_ksettings() for correct ops-locked use

[Jakub Kicinski <kuba@kernel.org>]

__ethtool_get_link_ksettings() is exported and called from sysfs
and many drivers. It invokes ethtool_ops->get_link_ksettings
so by our own docs it should be holding netdev lock for ops locked
devices. Looks like commit 2bcf4772e45a ("net: ethtool:
try to protect all callback with netdev instance lock")
missed adding the ops lock here.

There's a number of callers we need to fix up so let's add the
netif_get_link_ksettings() helper first, without any actual
locking changes (this commit is a nop).

Not treating this as a fix because I don't think any driver cares
at this point, but if we want to remove the rtnl_lock protection
this will become critical.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
v2:
 - split into multiple patches
---
 include/linux/ethtool.h |  2 ++
 net/ethtool/ioctl.c     | 17 ++++++++++++++---
 net/ethtool/linkinfo.c  |  4 ++--
 net/ethtool/linkmodes.c |  4 ++--
 4 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/include/linux/ethtool.h b/include/linux/ethtool.h
index 1cb0740ba331..f51346a6a686 100644
--- a/include/linux/ethtool.h
+++ b/include/linux/ethtool.h
@@ -325,6 +325,8 @@ struct ethtool_link_ksettings {
 extern int
 __ethtool_get_link_ksettings(struct net_device *dev,
 			     struct ethtool_link_ksettings *link_ksettings);
+int netif_get_link_ksettings(struct net_device *dev,
+			     struct ethtool_link_ksettings *link_ksettings);
 
 struct ethtool_keee {
 	__ETHTOOL_DECLARE_LINK_MODE_MASK(supported);
diff --git a/net/ethtool/ioctl.c b/net/ethtool/ioctl.c
index bd97f9b9bf18..49da873b673d 100644
--- a/net/ethtool/ioctl.c
+++ b/net/ethtool/ioctl.c
@@ -436,10 +436,10 @@ struct ethtool_link_usettings {
 };
 
 /* Internal kernel helper to query a device ethtool_link_settings. */
-int __ethtool_get_link_ksettings(struct net_device *dev,
-				 struct ethtool_link_ksettings *link_ksettings)
+int netif_get_link_ksettings(struct net_device *dev,
+			     struct ethtool_link_ksettings *link_ksettings)
 {
-	ASSERT_RTNL();
+	/* once callers fixed - assert ops locked */
 
 	if (!dev->ethtool_ops->get_link_ksettings)
 		return -EOPNOTSUPP;
@@ -450,6 +450,17 @@ int __ethtool_get_link_ksettings(struct net_device *dev,
 	memset(link_ksettings, 0, sizeof(*link_ksettings));
 	return dev->ethtool_ops->get_link_ksettings(dev, link_ksettings);
 }
+EXPORT_SYMBOL(netif_get_link_ksettings);
+
+/* Convenience helper for callers that hold only rtnl_lock(). */
+int __ethtool_get_link_ksettings(struct net_device *dev,
+				 struct ethtool_link_ksettings *link_ksettings)
+{
+	ASSERT_RTNL();
+
+	/* once callers fixed - take the ops lock around this call */
+	return netif_get_link_ksettings(dev, link_ksettings);
+}
 EXPORT_SYMBOL(__ethtool_get_link_ksettings);
 
 /* convert ethtool_link_usettings in user space to a kernel internal
diff --git a/net/ethtool/linkinfo.c b/net/ethtool/linkinfo.c
index 244ff92e2ff9..d5b3dbc53c5f 100644
--- a/net/ethtool/linkinfo.c
+++ b/net/ethtool/linkinfo.c
@@ -34,7 +34,7 @@ static int linkinfo_prepare_data(const struct ethnl_req_info *req_base,
 	ret = ethnl_ops_begin(dev);
 	if (ret < 0)
 		return ret;
-	ret = __ethtool_get_link_ksettings(dev, &data->ksettings);
+	ret = netif_get_link_ksettings(dev, &data->ksettings);
 	if (ret < 0)
 		GENL_SET_ERR_MSG(info, "failed to retrieve link settings");
 	ethnl_ops_complete(dev);
@@ -104,7 +104,7 @@ ethnl_set_linkinfo(struct ethnl_req_info *req_info, struct genl_info *info)
 	bool mod = false;
 	int ret;
 
-	ret = __ethtool_get_link_ksettings(dev, &ksettings);
+	ret = netif_get_link_ksettings(dev, &ksettings);
 	if (ret < 0) {
 		GENL_SET_ERR_MSG(info, "failed to retrieve link settings");
 		return ret;
diff --git a/net/ethtool/linkmodes.c b/net/ethtool/linkmodes.c
index 30d703531652..a6d32f0d9fcc 100644
--- a/net/ethtool/linkmodes.c
+++ b/net/ethtool/linkmodes.c
@@ -39,7 +39,7 @@ static int linkmodes_prepare_data(const struct ethnl_req_info *req_base,
 	if (ret < 0)
 		return ret;
 
-	ret = __ethtool_get_link_ksettings(dev, &data->ksettings);
+	ret = netif_get_link_ksettings(dev, &data->ksettings);
 	if (ret < 0) {
 		GENL_SET_ERR_MSG(info, "failed to retrieve link settings");
 		goto out;
@@ -324,7 +324,7 @@ ethnl_set_linkmodes(struct ethnl_req_info *req_info, struct genl_info *info)
 	bool mod = false;
 	int ret;
 
-	ret = __ethtool_get_link_ksettings(dev, &ksettings);
+	ret = netif_get_link_ksettings(dev, &ksettings);
 	if (ret < 0) {
 		GENL_SET_ERR_MSG(info, "failed to retrieve link settings");
 		return ret;
-- 
2.54.0