ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 226 insertions, 0 deletions

diff --git a/net/ethtool/linkstate.c b/net/ethtool/linkstate.c
new file mode 100644
index 000000000..24569e929
--- /dev/null
+++ b/net/ethtool/linkstate.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/phy.h>
+#include <linux/phylib_stubs.h>
+
+#include "common.h"
+#include "netlink.h"
+
+struct linkstate_req_info {
+	struct ethnl_req_info		base;
+};
+
+struct linkstate_reply_data {
+	struct ethnl_reply_data			base;
+	int					link;
+	int					sqi;
+	int					sqi_max;
+	struct ethtool_link_ext_stats		link_stats;
+	bool					link_ext_state_provided;
+	struct ethtool_link_ext_state_info	ethtool_link_ext_state_info;
+};
+
+#define LINKSTATE_REPDATA(__reply_base) \
+	container_of(__reply_base, struct linkstate_reply_data, base)
+
+const struct nla_policy ethnl_linkstate_get_policy[] = {
+	[ETHTOOL_A_LINKSTATE_HEADER]		=
+		NLA_POLICY_NESTED(ethnl_header_policy_stats),
+};
+
+static int linkstate_get_sqi(struct phy_device *phydev)
+{
+	int ret;
+
+	if (!phydev)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&phydev->lock);
+	if (!phydev->drv || !phydev->drv->get_sqi)
+		ret = -EOPNOTSUPP;
+	else if (!phydev->link)
+		ret = -ENETDOWN;
+	else
+		ret = phydev->drv->get_sqi(phydev);
+	mutex_unlock(&phydev->lock);
+
+	return ret;
+}
+
+static int linkstate_get_sqi_max(struct phy_device *phydev)
+{
+	int ret;
+
+	if (!phydev)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&phydev->lock);
+	if (!phydev->drv || !phydev->drv->get_sqi_max)
+		ret = -EOPNOTSUPP;
+	else if (!phydev->link)
+		ret = -ENETDOWN;
+	else
+		ret = phydev->drv->get_sqi_max(phydev);
+	mutex_unlock(&phydev->lock);
+
+	return ret;
+};
+
+static bool linkstate_sqi_critical_error(int sqi)
+{
+	return sqi < 0 && sqi != -EOPNOTSUPP && sqi != -ENETDOWN;
+}
+
+static bool linkstate_sqi_valid(struct linkstate_reply_data *data)
+{
+	return data->sqi >= 0 && data->sqi_max >= 0 &&
+	       data->sqi <= data->sqi_max;
+}
+
+static int linkstate_get_link_ext_state(struct net_device *dev,
+					struct linkstate_reply_data *data)
+{
+	int err;
+
+	if (!dev->ethtool_ops->get_link_ext_state)
+		return -EOPNOTSUPP;
+
+	err = dev->ethtool_ops->get_link_ext_state(dev, &data->ethtool_link_ext_state_info);
+	if (err)
+		return err;
+
+	data->link_ext_state_provided = true;
+
+	return 0;
+}
+
+static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
+				  struct ethnl_reply_data *reply_base,
+				  const struct genl_info *info)
+{
+	struct linkstate_reply_data *data = LINKSTATE_REPDATA(reply_base);
+	struct net_device *dev = reply_base->dev;
+	struct nlattr **tb = info->attrs;
+	struct phy_device *phydev;
+	int ret;
+
+	phydev = ethnl_req_get_phydev(req_base, tb, ETHTOOL_A_LINKSTATE_HEADER,
+				      info->extack);
+	if (IS_ERR(phydev))
+		return PTR_ERR(phydev);
+
+	ret = ethnl_ops_begin(dev);
+	if (ret < 0)
+		return ret;
+	data->link = __ethtool_get_link(dev);
+
+	ret = linkstate_get_sqi(phydev);
+	if (linkstate_sqi_critical_error(ret))
+		goto out;
+	data->sqi = ret;
+
+	ret = linkstate_get_sqi_max(phydev);
+	if (linkstate_sqi_critical_error(ret))
+		goto out;
+	data->sqi_max = ret;
+
+	if (dev->flags & IFF_UP) {
+		ret = linkstate_get_link_ext_state(dev, data);
+		if (ret < 0 && ret != -EOPNOTSUPP && ret != -ENODATA)
+			goto out;
+	}
+
+	ethtool_stats_init((u64 *)&data->link_stats,
+			   sizeof(data->link_stats) / 8);
+
+	if (req_base->flags & ETHTOOL_FLAG_STATS) {
+		if (phydev)
+			phy_ethtool_get_link_ext_stats(phydev,
+						       &data->link_stats);
+
+		if (dev->ethtool_ops->get_link_ext_stats)
+			dev->ethtool_ops->get_link_ext_stats(dev,
+							     &data->link_stats);
+	}
+
+	ret = 0;
+out:
+	ethnl_ops_complete(dev);
+	return ret;
+}
+
+static int linkstate_reply_size(const struct ethnl_req_info *req_base,
+				const struct ethnl_reply_data *reply_base)
+{
+	struct linkstate_reply_data *data = LINKSTATE_REPDATA(reply_base);
+	int len;
+
+	len = nla_total_size(sizeof(u8)) /* LINKSTATE_LINK */
+		+ 0;
+
+	if (linkstate_sqi_valid(data)) {
+		len += nla_total_size(sizeof(u32)); /* LINKSTATE_SQI */
+		len += nla_total_size(sizeof(u32)); /* LINKSTATE_SQI_MAX */
+	}
+
+	if (data->link_ext_state_provided)
+		len += nla_total_size(sizeof(u8)); /* LINKSTATE_EXT_STATE */
+
+	if (data->ethtool_link_ext_state_info.__link_ext_substate)
+		len += nla_total_size(sizeof(u8)); /* LINKSTATE_EXT_SUBSTATE */
+
+	if (data->link_stats.link_down_events != ETHTOOL_STAT_NOT_SET)
+		len += nla_total_size(sizeof(u32));
+
+	return len;
+}
+
+static int linkstate_fill_reply(struct sk_buff *skb,
+				const struct ethnl_req_info *req_base,
+				const struct ethnl_reply_data *reply_base)
+{
+	struct linkstate_reply_data *data = LINKSTATE_REPDATA(reply_base);
+
+	if (data->link >= 0 &&
+	    nla_put_u8(skb, ETHTOOL_A_LINKSTATE_LINK, !!data->link))
+		return -EMSGSIZE;
+
+	if (linkstate_sqi_valid(data)) {
+		if (nla_put_u32(skb, ETHTOOL_A_LINKSTATE_SQI, data->sqi))
+			return -EMSGSIZE;
+
+		if (nla_put_u32(skb, ETHTOOL_A_LINKSTATE_SQI_MAX,
+				data->sqi_max))
+			return -EMSGSIZE;
+	}
+
+	if (data->link_ext_state_provided) {
+		if (nla_put_u8(skb, ETHTOOL_A_LINKSTATE_EXT_STATE,
+			       data->ethtool_link_ext_state_info.link_ext_state))
+			return -EMSGSIZE;
+
+		if (data->ethtool_link_ext_state_info.__link_ext_substate &&
+		    nla_put_u8(skb, ETHTOOL_A_LINKSTATE_EXT_SUBSTATE,
+			       data->ethtool_link_ext_state_info.__link_ext_substate))
+			return -EMSGSIZE;
+	}
+
+	if (data->link_stats.link_down_events != ETHTOOL_STAT_NOT_SET)
+		if (nla_put_u32(skb, ETHTOOL_A_LINKSTATE_EXT_DOWN_CNT,
+				data->link_stats.link_down_events))
+			return -EMSGSIZE;
+
+	return 0;
+}
+
+const struct ethnl_request_ops ethnl_linkstate_request_ops = {
+	.request_cmd		= ETHTOOL_MSG_LINKSTATE_GET,
+	.reply_cmd		= ETHTOOL_MSG_LINKSTATE_GET_REPLY,
+	.hdr_attr		= ETHTOOL_A_LINKSTATE_HEADER,
+	.req_info_size		= sizeof(struct linkstate_req_info),
+	.reply_data_size	= sizeof(struct linkstate_reply_data),
+
+	.prepare_data		= linkstate_prepare_data,
+	.reply_size		= linkstate_reply_size,
+	.fill_reply		= linkstate_fill_reply,
+};