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, 304 insertions, 0 deletions

diff --git a/net/wireless/debugfs.c b/net/wireless/debugfs.c
new file mode 100644
index 000000000..f9e7fff1e
--- /dev/null
+++ b/net/wireless/debugfs.c
@@ -0,0 +1,304 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * cfg80211 debugfs
+ *
+ * Copyright 2009	Luis R. Rodriguez <lrodriguez@atheros.com>
+ * Copyright 2007	Johannes Berg <johannes@sipsolutions.net>
+ * Copyright (C) 2023 Intel Corporation
+ */
+
+#include <linux/slab.h>
+#include "core.h"
+#include "debugfs.h"
+
+#define DEBUGFS_READONLY_FILE(name, buflen, fmt, value...)		\
+static ssize_t name## _read(struct file *file, char __user *userbuf,	\
+			    size_t count, loff_t *ppos)			\
+{									\
+	struct wiphy *wiphy = file->private_data;			\
+	char buf[buflen];						\
+	int res;							\
+									\
+	res = scnprintf(buf, buflen, fmt "\n", ##value);		\
+	return simple_read_from_buffer(userbuf, count, ppos, buf, res);	\
+}									\
+									\
+static const struct file_operations name## _ops = {			\
+	.read = name## _read,						\
+	.open = simple_open,						\
+	.llseek = generic_file_llseek,					\
+}
+
+#define DEBUGFS_RADIO_READONLY_FILE(name, buflen, fmt, value...)	\
+static ssize_t name## _read(struct file *file, char __user *userbuf,	\
+			    size_t count, loff_t *ppos)			\
+{									\
+	struct wiphy_radio_cfg *radio_cfg = file->private_data;		\
+	char buf[buflen];						\
+	int res;							\
+									\
+	res = scnprintf(buf, buflen, fmt "\n", ##value);		\
+	return simple_read_from_buffer(userbuf, count, ppos, buf, res);	\
+}									\
+									\
+static const struct file_operations name## _ops = {			\
+	.read = name## _read,						\
+	.open = simple_open,						\
+	.llseek = generic_file_llseek,					\
+}
+
+DEBUGFS_READONLY_FILE(rts_threshold, 20, "%d",
+		      wiphy->rts_threshold);
+DEBUGFS_READONLY_FILE(fragmentation_threshold, 20, "%d",
+		      wiphy->frag_threshold);
+DEBUGFS_READONLY_FILE(short_retry_limit, 20, "%d",
+		      wiphy->retry_short);
+DEBUGFS_READONLY_FILE(long_retry_limit, 20, "%d",
+		      wiphy->retry_long);
+
+DEBUGFS_RADIO_READONLY_FILE(radio_rts_threshold, 20, "%d",
+			    radio_cfg->rts_threshold);
+
+static int ht_print_chan(struct ieee80211_channel *chan,
+			 char *buf, int buf_size, int offset)
+{
+	if (WARN_ON(offset > buf_size))
+		return 0;
+
+	if (chan->flags & IEEE80211_CHAN_DISABLED)
+		return scnprintf(buf + offset,
+				 buf_size - offset,
+				 "%d Disabled\n",
+				 chan->center_freq);
+
+	return scnprintf(buf + offset,
+			 buf_size - offset,
+			 "%d HT40 %c%c\n",
+			 chan->center_freq,
+			 (chan->flags & IEEE80211_CHAN_NO_HT40MINUS) ?
+				' ' : '-',
+			 (chan->flags & IEEE80211_CHAN_NO_HT40PLUS) ?
+				' ' : '+');
+}
+
+static ssize_t ht40allow_map_read(struct file *file,
+				  char __user *user_buf,
+				  size_t count, loff_t *ppos)
+{
+	struct wiphy *wiphy = file->private_data;
+	char *buf;
+	unsigned int offset = 0, buf_size = PAGE_SIZE, i;
+	enum nl80211_band band;
+	struct ieee80211_supported_band *sband;
+	ssize_t r;
+
+	buf = kzalloc(buf_size, GFP_KERNEL);
+	if (!buf)
+		return -ENOMEM;
+
+	for (band = 0; band < NUM_NL80211_BANDS; band++) {
+		sband = wiphy->bands[band];
+		if (!sband)
+			continue;
+		for (i = 0; i < sband->n_channels; i++)
+			offset += ht_print_chan(&sband->channels[i],
+						buf, buf_size, offset);
+	}
+
+	r = simple_read_from_buffer(user_buf, count, ppos, buf, offset);
+
+	kfree(buf);
+
+	return r;
+}
+
+static const struct file_operations ht40allow_map_ops = {
+	.read = ht40allow_map_read,
+	.open = simple_open,
+	.llseek = default_llseek,
+};
+
+#define DEBUGFS_ADD(name)						\
+	debugfs_create_file(#name, 0444, phyd, &rdev->wiphy, &name## _ops)
+
+#define DEBUGFS_RADIO_ADD(name, radio_idx)				\
+	debugfs_create_file(#name, 0444, radiod,			\
+			    &rdev->wiphy.radio_cfg[radio_idx],		\
+			    &name## _ops)
+
+void cfg80211_debugfs_rdev_add(struct cfg80211_registered_device *rdev)
+{
+	struct dentry *phyd = rdev->wiphy.debugfsdir;
+	struct dentry *radiod;
+	u8 i;
+
+	DEBUGFS_ADD(rts_threshold);
+	DEBUGFS_ADD(fragmentation_threshold);
+	DEBUGFS_ADD(short_retry_limit);
+	DEBUGFS_ADD(long_retry_limit);
+	DEBUGFS_ADD(ht40allow_map);
+
+	for (i = 0; i < rdev->wiphy.n_radio; i++) {
+		radiod = rdev->wiphy.radio_cfg[i].radio_debugfsdir;
+		DEBUGFS_RADIO_ADD(radio_rts_threshold, i);
+	}
+}
+
+struct debugfs_read_work {
+	struct wiphy_work work;
+	ssize_t (*handler)(struct wiphy *wiphy,
+			   struct file *file,
+			   char *buf,
+			   size_t count,
+			   void *data);
+	struct wiphy *wiphy;
+	struct file *file;
+	char *buf;
+	size_t bufsize;
+	void *data;
+	ssize_t ret;
+	struct completion completion;
+};
+
+static void wiphy_locked_debugfs_read_work(struct wiphy *wiphy,
+					   struct wiphy_work *work)
+{
+	struct debugfs_read_work *w = container_of(work, typeof(*w), work);
+
+	w->ret = w->handler(w->wiphy, w->file, w->buf, w->bufsize, w->data);
+	complete(&w->completion);
+}
+
+static void wiphy_locked_debugfs_read_cancel(struct dentry *dentry,
+					     void *data)
+{
+	struct debugfs_read_work *w = data;
+
+	wiphy_work_cancel(w->wiphy, &w->work);
+	complete(&w->completion);
+}
+
+ssize_t wiphy_locked_debugfs_read(struct wiphy *wiphy, struct file *file,
+				  char *buf, size_t bufsize,
+				  char __user *userbuf, size_t count,
+				  loff_t *ppos,
+				  ssize_t (*handler)(struct wiphy *wiphy,
+						     struct file *file,
+						     char *buf,
+						     size_t bufsize,
+						     void *data),
+				  void *data)
+{
+	struct debugfs_read_work work = {
+		.handler = handler,
+		.wiphy = wiphy,
+		.file = file,
+		.buf = buf,
+		.bufsize = bufsize,
+		.data = data,
+		.ret = -ENODEV,
+		.completion = COMPLETION_INITIALIZER_ONSTACK(work.completion),
+	};
+	struct debugfs_cancellation cancellation = {
+		.cancel = wiphy_locked_debugfs_read_cancel,
+		.cancel_data = &work,
+	};
+
+	/* don't leak stack data or whatever */
+	memset(buf, 0, bufsize);
+
+	wiphy_work_init(&work.work, wiphy_locked_debugfs_read_work);
+	wiphy_work_queue(wiphy, &work.work);
+
+	debugfs_enter_cancellation(file, &cancellation);
+	wait_for_completion(&work.completion);
+	debugfs_leave_cancellation(file, &cancellation);
+
+	if (work.ret < 0)
+		return work.ret;
+
+	if (WARN_ON(work.ret > bufsize))
+		return -EINVAL;
+
+	return simple_read_from_buffer(userbuf, count, ppos, buf, work.ret);
+}
+EXPORT_SYMBOL_GPL(wiphy_locked_debugfs_read);
+
+struct debugfs_write_work {
+	struct wiphy_work work;
+	ssize_t (*handler)(struct wiphy *wiphy,
+			   struct file *file,
+			   char *buf,
+			   size_t count,
+			   void *data);
+	struct wiphy *wiphy;
+	struct file *file;
+	char *buf;
+	size_t count;
+	void *data;
+	ssize_t ret;
+	struct completion completion;
+};
+
+static void wiphy_locked_debugfs_write_work(struct wiphy *wiphy,
+					    struct wiphy_work *work)
+{
+	struct debugfs_write_work *w = container_of(work, typeof(*w), work);
+
+	w->ret = w->handler(w->wiphy, w->file, w->buf, w->count, w->data);
+	complete(&w->completion);
+}
+
+static void wiphy_locked_debugfs_write_cancel(struct dentry *dentry,
+					      void *data)
+{
+	struct debugfs_write_work *w = data;
+
+	wiphy_work_cancel(w->wiphy, &w->work);
+	complete(&w->completion);
+}
+
+ssize_t wiphy_locked_debugfs_write(struct wiphy *wiphy,
+				   struct file *file, char *buf, size_t bufsize,
+				   const char __user *userbuf, size_t count,
+				   ssize_t (*handler)(struct wiphy *wiphy,
+						      struct file *file,
+						      char *buf,
+						      size_t count,
+						      void *data),
+				   void *data)
+{
+	struct debugfs_write_work work = {
+		.handler = handler,
+		.wiphy = wiphy,
+		.file = file,
+		.buf = buf,
+		.count = count,
+		.data = data,
+		.ret = -ENODEV,
+		.completion = COMPLETION_INITIALIZER_ONSTACK(work.completion),
+	};
+	struct debugfs_cancellation cancellation = {
+		.cancel = wiphy_locked_debugfs_write_cancel,
+		.cancel_data = &work,
+	};
+
+	/* mostly used for strings so enforce NUL-termination for safety */
+	if (count >= bufsize)
+		return -EINVAL;
+
+	memset(buf, 0, bufsize);
+
+	if (copy_from_user(buf, userbuf, count))
+		return -EFAULT;
+
+	wiphy_work_init(&work.work, wiphy_locked_debugfs_write_work);
+	wiphy_work_queue(wiphy, &work.work);
+
+	debugfs_enter_cancellation(file, &cancellation);
+	wait_for_completion(&work.completion);
+	debugfs_leave_cancellation(file, &cancellation);
+
+	return work.ret;
+}
+EXPORT_SYMBOL_GPL(wiphy_locked_debugfs_write);