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, 231 insertions, 0 deletions

diff --git a/drivers/net/netdevsim/health.c b/drivers/net/netdevsim/health.c
new file mode 100644
index 000000000..3bd0e7a48
--- /dev/null
+++ b/drivers/net/netdevsim/health.c
@@ -0,0 +1,231 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2019 Mellanox Technologies. All rights reserved */
+
+#include <linux/debugfs.h>
+#include <linux/err.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+#include "netdevsim.h"
+
+static int
+nsim_dev_empty_reporter_dump(struct devlink_health_reporter *reporter,
+			     struct devlink_fmsg *fmsg, void *priv_ctx,
+			     struct netlink_ext_ack *extack)
+{
+	return 0;
+}
+
+static int
+nsim_dev_empty_reporter_diagnose(struct devlink_health_reporter *reporter,
+				 struct devlink_fmsg *fmsg,
+				 struct netlink_ext_ack *extack)
+{
+	return 0;
+}
+
+static const
+struct devlink_health_reporter_ops nsim_dev_empty_reporter_ops = {
+	.name = "empty",
+	.dump = nsim_dev_empty_reporter_dump,
+	.diagnose = nsim_dev_empty_reporter_diagnose,
+};
+
+struct nsim_dev_dummy_reporter_ctx {
+	char *break_msg;
+};
+
+static int
+nsim_dev_dummy_reporter_recover(struct devlink_health_reporter *reporter,
+				void *priv_ctx,
+				struct netlink_ext_ack *extack)
+{
+	struct nsim_dev_health *health = devlink_health_reporter_priv(reporter);
+	struct nsim_dev_dummy_reporter_ctx *ctx = priv_ctx;
+
+	if (health->fail_recover) {
+		/* For testing purposes, user set debugfs fail_recover
+		 * value to true. Fail right away.
+		 */
+		NL_SET_ERR_MSG_MOD(extack, "User setup the recover to fail for testing purposes");
+		return -EINVAL;
+	}
+	if (ctx) {
+		kfree(health->recovered_break_msg);
+		health->recovered_break_msg = kstrdup(ctx->break_msg,
+						      GFP_KERNEL);
+		if (!health->recovered_break_msg)
+			return -ENOMEM;
+	}
+	return 0;
+}
+
+static int nsim_dev_dummy_fmsg_put(struct devlink_fmsg *fmsg, u32 binary_len)
+{
+	char *binary;
+	int i;
+
+	devlink_fmsg_bool_pair_put(fmsg, "test_bool", true);
+	devlink_fmsg_u8_pair_put(fmsg, "test_u8", 1);
+	devlink_fmsg_u32_pair_put(fmsg, "test_u32", 3);
+	devlink_fmsg_u64_pair_put(fmsg, "test_u64", 4);
+	devlink_fmsg_string_pair_put(fmsg, "test_string", "somestring");
+
+	binary = kmalloc(binary_len, GFP_KERNEL | __GFP_NOWARN);
+	if (!binary)
+		return -ENOMEM;
+	get_random_bytes(binary, binary_len);
+	devlink_fmsg_binary_pair_put(fmsg, "test_binary", binary, binary_len);
+	kfree(binary);
+
+	devlink_fmsg_pair_nest_start(fmsg, "test_nest");
+	devlink_fmsg_obj_nest_start(fmsg);
+	devlink_fmsg_bool_pair_put(fmsg, "nested_test_bool", false);
+	devlink_fmsg_u8_pair_put(fmsg, "nested_test_u8", false);
+	devlink_fmsg_obj_nest_end(fmsg);
+	devlink_fmsg_pair_nest_end(fmsg);
+	devlink_fmsg_arr_pair_nest_end(fmsg);
+	devlink_fmsg_arr_pair_nest_start(fmsg, "test_u32_array");
+
+	for (i = 0; i < 10; i++)
+		devlink_fmsg_u32_put(fmsg, i);
+	devlink_fmsg_arr_pair_nest_end(fmsg);
+	devlink_fmsg_arr_pair_nest_start(fmsg, "test_array_of_objects");
+
+	for (i = 0; i < 10; i++) {
+		devlink_fmsg_obj_nest_start(fmsg);
+		devlink_fmsg_bool_pair_put(fmsg, "in_array_nested_test_bool",
+					   false);
+		devlink_fmsg_u8_pair_put(fmsg, "in_array_nested_test_u8", i);
+		devlink_fmsg_obj_nest_end(fmsg);
+	}
+	devlink_fmsg_arr_pair_nest_end(fmsg);
+
+	return 0;
+}
+
+static int
+nsim_dev_dummy_reporter_dump(struct devlink_health_reporter *reporter,
+			     struct devlink_fmsg *fmsg, void *priv_ctx,
+			     struct netlink_ext_ack *extack)
+{
+	struct nsim_dev_health *health = devlink_health_reporter_priv(reporter);
+	struct nsim_dev_dummy_reporter_ctx *ctx = priv_ctx;
+
+	if (ctx)
+		devlink_fmsg_string_pair_put(fmsg, "break_message", ctx->break_msg);
+
+	return nsim_dev_dummy_fmsg_put(fmsg, health->binary_len);
+}
+
+static int
+nsim_dev_dummy_reporter_diagnose(struct devlink_health_reporter *reporter,
+				 struct devlink_fmsg *fmsg,
+				 struct netlink_ext_ack *extack)
+{
+	struct nsim_dev_health *health = devlink_health_reporter_priv(reporter);
+
+	if (health->recovered_break_msg)
+		devlink_fmsg_string_pair_put(fmsg, "recovered_break_message",
+					     health->recovered_break_msg);
+
+	return nsim_dev_dummy_fmsg_put(fmsg, health->binary_len);
+}
+
+static const
+struct devlink_health_reporter_ops nsim_dev_dummy_reporter_ops = {
+	.name = "dummy",
+	.recover = nsim_dev_dummy_reporter_recover,
+	.dump = nsim_dev_dummy_reporter_dump,
+	.diagnose = nsim_dev_dummy_reporter_diagnose,
+};
+
+static ssize_t nsim_dev_health_break_write(struct file *file,
+					   const char __user *data,
+					   size_t count, loff_t *ppos)
+{
+	struct nsim_dev_health *health = file->private_data;
+	struct nsim_dev_dummy_reporter_ctx ctx;
+	char *break_msg;
+	int err;
+
+	if (count == 0 || count > PAGE_SIZE)
+		return -EINVAL;
+	break_msg = memdup_user_nul(data, count);
+	if (IS_ERR(break_msg))
+		return PTR_ERR(break_msg);
+
+	if (break_msg[count - 1] == '\n')
+		break_msg[count - 1] = '\0';
+
+	ctx.break_msg = break_msg;
+	err = devlink_health_report(health->dummy_reporter, break_msg, &ctx);
+	if (err)
+		goto out;
+
+out:
+	kfree(break_msg);
+	return err ?: count;
+}
+
+static const struct file_operations nsim_dev_health_break_fops = {
+	.open = simple_open,
+	.write = nsim_dev_health_break_write,
+	.llseek = generic_file_llseek,
+	.owner = THIS_MODULE,
+};
+
+int nsim_dev_health_init(struct nsim_dev *nsim_dev, struct devlink *devlink)
+{
+	struct nsim_dev_health *health = &nsim_dev->health;
+	int err;
+
+	health->empty_reporter =
+		devl_health_reporter_create(devlink,
+					    &nsim_dev_empty_reporter_ops,
+					    health);
+	if (IS_ERR(health->empty_reporter))
+		return PTR_ERR(health->empty_reporter);
+
+	health->dummy_reporter =
+		devl_health_reporter_create(devlink,
+					    &nsim_dev_dummy_reporter_ops,
+					    health);
+	if (IS_ERR(health->dummy_reporter)) {
+		err = PTR_ERR(health->dummy_reporter);
+		goto err_empty_reporter_destroy;
+	}
+
+	health->ddir = debugfs_create_dir("health", nsim_dev->ddir);
+	if (IS_ERR(health->ddir)) {
+		err = PTR_ERR(health->ddir);
+		goto err_dummy_reporter_destroy;
+	}
+
+	health->recovered_break_msg = NULL;
+	debugfs_create_file("break_health", 0200, health->ddir, health,
+			    &nsim_dev_health_break_fops);
+	health->binary_len = 16;
+	debugfs_create_u32("binary_len", 0600, health->ddir,
+			   &health->binary_len);
+	health->fail_recover = false;
+	debugfs_create_bool("fail_recover", 0600, health->ddir,
+			    &health->fail_recover);
+	return 0;
+
+err_dummy_reporter_destroy:
+	devl_health_reporter_destroy(health->dummy_reporter);
+err_empty_reporter_destroy:
+	devl_health_reporter_destroy(health->empty_reporter);
+	return err;
+}
+
+void nsim_dev_health_exit(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_health *health = &nsim_dev->health;
+
+	debugfs_remove_recursive(health->ddir);
+	kfree(health->recovered_break_msg);
+	devl_health_reporter_destroy(health->dummy_reporter);
+	devl_health_reporter_destroy(health->empty_reporter);
+}