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, 74 insertions, 0 deletions

diff --git a/net/wireless/ap.c b/net/wireless/ap.c
new file mode 100644
index 000000000..9a9a87080
--- /dev/null
+++ b/net/wireless/ap.c
@@ -0,0 +1,74 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Parts of this file are
+ * Copyright (C) 2022-2023 Intel Corporation
+ */
+#include <linux/ieee80211.h>
+#include <linux/export.h>
+#include <net/cfg80211.h>
+#include "nl80211.h"
+#include "core.h"
+#include "rdev-ops.h"
+
+
+static int ___cfg80211_stop_ap(struct cfg80211_registered_device *rdev,
+			       struct net_device *dev, unsigned int link_id,
+			       bool notify)
+{
+	struct wireless_dev *wdev = dev->ieee80211_ptr;
+	int err;
+
+	lockdep_assert_wiphy(wdev->wiphy);
+
+	if (!rdev->ops->stop_ap)
+		return -EOPNOTSUPP;
+
+	if (dev->ieee80211_ptr->iftype != NL80211_IFTYPE_AP &&
+	    dev->ieee80211_ptr->iftype != NL80211_IFTYPE_P2P_GO)
+		return -EOPNOTSUPP;
+
+	if (!wdev->links[link_id].ap.beacon_interval)
+		return -ENOENT;
+
+	err = rdev_stop_ap(rdev, dev, link_id);
+	if (!err) {
+		wdev->conn_owner_nlportid = 0;
+		wdev->links[link_id].ap.beacon_interval = 0;
+		memset(&wdev->links[link_id].ap.chandef, 0,
+		       sizeof(wdev->links[link_id].ap.chandef));
+		wdev->u.ap.ssid_len = 0;
+		rdev_set_qos_map(rdev, dev, NULL);
+		if (notify)
+			nl80211_send_ap_stopped(wdev, link_id);
+
+		/* Should we apply the grace period during beaconing interface
+		 * shutdown also?
+		 */
+		cfg80211_sched_dfs_chan_update(rdev);
+	}
+
+	schedule_work(&cfg80211_disconnect_work);
+
+	return err;
+}
+
+int cfg80211_stop_ap(struct cfg80211_registered_device *rdev,
+		     struct net_device *dev, int link_id,
+		     bool notify)
+{
+	unsigned int link;
+	int ret = 0;
+
+	if (link_id >= 0)
+		return ___cfg80211_stop_ap(rdev, dev, link_id, notify);
+
+	for_each_valid_link(dev->ieee80211_ptr, link) {
+		int ret1 = ___cfg80211_stop_ap(rdev, dev, link, notify);
+
+		if (ret1)
+			ret = ret1;
+		/* try the next one also if one errored */
+	}
+
+	return ret;
+}