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, 462 insertions, 0 deletions

diff --git a/lib/fault-inject.c b/lib/fault-inject.c
new file mode 100644
index 000000000..999053fa1
--- /dev/null
+++ b/lib/fault-inject.c
@@ -0,0 +1,462 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/prandom.h>
+#include <linux/debugfs.h>
+#include <linux/sched.h>
+#include <linux/stat.h>
+#include <linux/types.h>
+#include <linux/fs.h>
+#include <linux/export.h>
+#include <linux/interrupt.h>
+#include <linux/stacktrace.h>
+#include <linux/fault-inject.h>
+
+/*
+ * The should_fail() functions use prandom instead of the normal Linux RNG
+ * since they don't need cryptographically secure random numbers.
+ */
+static DEFINE_PER_CPU(struct rnd_state, fault_rnd_state);
+
+static u32 fault_prandom_u32_below_100(void)
+{
+	struct rnd_state *state;
+	u32 res;
+
+	state = &get_cpu_var(fault_rnd_state);
+	res = prandom_u32_state(state);
+	put_cpu_var(fault_rnd_state);
+
+	return res % 100;
+}
+
+/*
+ * setup_fault_attr() is a helper function for various __setup handlers, so it
+ * returns 0 on error, because that is what __setup handlers do.
+ */
+int setup_fault_attr(struct fault_attr *attr, char *str)
+{
+	unsigned long probability;
+	unsigned long interval;
+	int times;
+	int space;
+
+	/* "<interval>,<probability>,<space>,<times>" */
+	if (sscanf(str, "%lu,%lu,%d,%d",
+			&interval, &probability, &space, &times) < 4) {
+		printk(KERN_WARNING
+			"FAULT_INJECTION: failed to parse arguments\n");
+		return 0;
+	}
+
+	prandom_init_once(&fault_rnd_state);
+
+	attr->probability = probability;
+	attr->interval = interval;
+	atomic_set(&attr->times, times);
+	atomic_set(&attr->space, space);
+
+	return 1;
+}
+EXPORT_SYMBOL_GPL(setup_fault_attr);
+
+static void fail_dump(struct fault_attr *attr)
+{
+	if (attr->verbose > 0 && __ratelimit(&attr->ratelimit_state)) {
+		printk(KERN_NOTICE "FAULT_INJECTION: forcing a failure.\n"
+		       "name %pd, interval %lu, probability %lu, "
+		       "space %d, times %d\n", attr->dname,
+		       attr->interval, attr->probability,
+		       atomic_read(&attr->space),
+		       atomic_read(&attr->times));
+		if (attr->verbose > 1)
+			dump_stack();
+	}
+}
+
+#define atomic_dec_not_zero(v)		atomic_add_unless((v), -1, 0)
+
+static bool fail_task(struct fault_attr *attr, struct task_struct *task)
+{
+	return in_task() && task->make_it_fail;
+}
+
+#define MAX_STACK_TRACE_DEPTH 32
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+static bool fail_stacktrace(struct fault_attr *attr)
+{
+	int depth = attr->stacktrace_depth;
+	unsigned long entries[MAX_STACK_TRACE_DEPTH];
+	int n, nr_entries;
+	bool found = (attr->require_start == 0 && attr->require_end == ULONG_MAX);
+
+	if (depth == 0 || (found && !attr->reject_start && !attr->reject_end))
+		return found;
+
+	nr_entries = stack_trace_save(entries, depth, 1);
+	for (n = 0; n < nr_entries; n++) {
+		if (attr->reject_start <= entries[n] &&
+			       entries[n] < attr->reject_end)
+			return false;
+		if (attr->require_start <= entries[n] &&
+			       entries[n] < attr->require_end)
+			found = true;
+	}
+	return found;
+}
+
+#else
+
+static inline bool fail_stacktrace(struct fault_attr *attr)
+{
+	return true;
+}
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+/*
+ * This code is stolen from failmalloc-1.0
+ * http://www.nongnu.org/failmalloc/
+ */
+
+bool should_fail_ex(struct fault_attr *attr, ssize_t size, int flags)
+{
+	bool stack_checked = false;
+
+	if (in_task()) {
+		unsigned int fail_nth = READ_ONCE(current->fail_nth);
+
+		if (fail_nth) {
+			if (!fail_stacktrace(attr))
+				return false;
+
+			stack_checked = true;
+			fail_nth--;
+			WRITE_ONCE(current->fail_nth, fail_nth);
+			if (!fail_nth)
+				goto fail;
+
+			return false;
+		}
+	}
+
+	/* No need to check any other properties if the probability is 0 */
+	if (attr->probability == 0)
+		return false;
+
+	if (attr->task_filter && !fail_task(attr, current))
+		return false;
+
+	if (atomic_read(&attr->times) == 0)
+		return false;
+
+	if (!stack_checked && !fail_stacktrace(attr))
+		return false;
+
+	if (atomic_read(&attr->space) > size) {
+		atomic_sub(size, &attr->space);
+		return false;
+	}
+
+	if (attr->interval > 1) {
+		attr->count++;
+		if (attr->count % attr->interval)
+			return false;
+	}
+
+	if (attr->probability <= fault_prandom_u32_below_100())
+		return false;
+
+fail:
+	if (!(flags & FAULT_NOWARN))
+		fail_dump(attr);
+
+	if (atomic_read(&attr->times) != -1)
+		atomic_dec_not_zero(&attr->times);
+
+	return true;
+}
+
+bool should_fail(struct fault_attr *attr, ssize_t size)
+{
+	return should_fail_ex(attr, size, 0);
+}
+EXPORT_SYMBOL_GPL(should_fail);
+
+#ifdef CONFIG_FAULT_INJECTION_DEBUG_FS
+
+static int debugfs_ul_set(void *data, u64 val)
+{
+	*(unsigned long *)data = val;
+	return 0;
+}
+
+static int debugfs_ul_get(void *data, u64 *val)
+{
+	*val = *(unsigned long *)data;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_ul, debugfs_ul_get, debugfs_ul_set, "%llu\n");
+
+static void debugfs_create_ul(const char *name, umode_t mode,
+			      struct dentry *parent, unsigned long *value)
+{
+	debugfs_create_file(name, mode, parent, value, &fops_ul);
+}
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+static int debugfs_stacktrace_depth_set(void *data, u64 val)
+{
+	*(unsigned long *)data =
+		min_t(unsigned long, val, MAX_STACK_TRACE_DEPTH);
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_stacktrace_depth, debugfs_ul_get,
+			debugfs_stacktrace_depth_set, "%llu\n");
+
+static void debugfs_create_stacktrace_depth(const char *name, umode_t mode,
+					    struct dentry *parent,
+					    unsigned long *value)
+{
+	debugfs_create_file(name, mode, parent, value, &fops_stacktrace_depth);
+}
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+struct dentry *fault_create_debugfs_attr(const char *name,
+			struct dentry *parent, struct fault_attr *attr)
+{
+	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+	struct dentry *dir;
+
+	dir = debugfs_create_dir(name, parent);
+	if (IS_ERR(dir))
+		return dir;
+
+	prandom_init_once(&fault_rnd_state);
+
+	debugfs_create_ul("probability", mode, dir, &attr->probability);
+	debugfs_create_ul("interval", mode, dir, &attr->interval);
+	debugfs_create_atomic_t("times", mode, dir, &attr->times);
+	debugfs_create_atomic_t("space", mode, dir, &attr->space);
+	debugfs_create_ul("verbose", mode, dir, &attr->verbose);
+	debugfs_create_u32("verbose_ratelimit_interval_ms", mode, dir,
+			   &attr->ratelimit_state.interval);
+	debugfs_create_u32("verbose_ratelimit_burst", mode, dir,
+			   &attr->ratelimit_state.burst);
+	debugfs_create_bool("task-filter", mode, dir, &attr->task_filter);
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+	debugfs_create_stacktrace_depth("stacktrace-depth", mode, dir,
+					&attr->stacktrace_depth);
+	debugfs_create_xul("require-start", mode, dir, &attr->require_start);
+	debugfs_create_xul("require-end", mode, dir, &attr->require_end);
+	debugfs_create_xul("reject-start", mode, dir, &attr->reject_start);
+	debugfs_create_xul("reject-end", mode, dir, &attr->reject_end);
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+	attr->dname = dget(dir);
+	return dir;
+}
+EXPORT_SYMBOL_GPL(fault_create_debugfs_attr);
+
+#endif /* CONFIG_FAULT_INJECTION_DEBUG_FS */
+
+#ifdef CONFIG_FAULT_INJECTION_CONFIGFS
+
+/* These configfs attribute utilities are copied from drivers/block/null_blk/main.c */
+
+static ssize_t fault_uint_attr_show(unsigned int val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t fault_ulong_attr_show(unsigned long val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%lu\n", val);
+}
+
+static ssize_t fault_bool_attr_show(bool val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%u\n", val);
+}
+
+static ssize_t fault_atomic_t_attr_show(atomic_t val, char *page)
+{
+	return snprintf(page, PAGE_SIZE, "%d\n", atomic_read(&val));
+}
+
+static ssize_t fault_uint_attr_store(unsigned int *val, const char *page, size_t count)
+{
+	unsigned int tmp;
+	int result;
+
+	result = kstrtouint(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	*val = tmp;
+	return count;
+}
+
+static ssize_t fault_ulong_attr_store(unsigned long *val, const char *page, size_t count)
+{
+	int result;
+	unsigned long tmp;
+
+	result = kstrtoul(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	*val = tmp;
+	return count;
+}
+
+static ssize_t fault_bool_attr_store(bool *val, const char *page, size_t count)
+{
+	bool tmp;
+	int result;
+
+	result = kstrtobool(page, &tmp);
+	if (result < 0)
+		return result;
+
+	*val = tmp;
+	return count;
+}
+
+static ssize_t fault_atomic_t_attr_store(atomic_t *val, const char *page, size_t count)
+{
+	int tmp;
+	int result;
+
+	result = kstrtoint(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	atomic_set(val, tmp);
+	return count;
+}
+
+#define CONFIGFS_ATTR_NAMED(_pfx, _name, _attr_name)	\
+static struct configfs_attribute _pfx##attr_##_name = {	\
+	.ca_name	= _attr_name,			\
+	.ca_mode	= 0644,				\
+	.ca_owner	= THIS_MODULE,			\
+	.show		= _pfx##_name##_show,		\
+	.store		= _pfx##_name##_store,		\
+}
+
+static struct fault_config *to_fault_config(struct config_item *item)
+{
+	return container_of(to_config_group(item), struct fault_config, group);
+}
+
+#define FAULT_CONFIGFS_ATTR_NAMED(NAME, ATTR_NAME, MEMBER, TYPE)				\
+static ssize_t fault_##NAME##_show(struct config_item *item, char *page)			\
+{												\
+	return fault_##TYPE##_attr_show(to_fault_config(item)->attr.MEMBER, page);		\
+}												\
+static ssize_t fault_##NAME##_store(struct config_item *item, const char *page, size_t count)	\
+{												\
+	struct fault_config *config = to_fault_config(item);					\
+	return fault_##TYPE##_attr_store(&config->attr.MEMBER, page, count);			\
+}												\
+CONFIGFS_ATTR_NAMED(fault_, NAME, ATTR_NAME)
+
+#define FAULT_CONFIGFS_ATTR(NAME, TYPE)	\
+	FAULT_CONFIGFS_ATTR_NAMED(NAME, __stringify(NAME), NAME, TYPE)
+
+FAULT_CONFIGFS_ATTR(probability, ulong);
+FAULT_CONFIGFS_ATTR(interval, ulong);
+FAULT_CONFIGFS_ATTR(times, atomic_t);
+FAULT_CONFIGFS_ATTR(space, atomic_t);
+FAULT_CONFIGFS_ATTR(verbose, ulong);
+FAULT_CONFIGFS_ATTR_NAMED(ratelimit_interval, "verbose_ratelimit_interval_ms",
+		ratelimit_state.interval, uint);
+FAULT_CONFIGFS_ATTR_NAMED(ratelimit_burst, "verbose_ratelimit_burst",
+		ratelimit_state.burst, uint);
+FAULT_CONFIGFS_ATTR_NAMED(task_filter, "task-filter", task_filter, bool);
+
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+
+static ssize_t fault_stacktrace_depth_show(struct config_item *item, char *page)
+{
+	return fault_ulong_attr_show(to_fault_config(item)->attr.stacktrace_depth, page);
+}
+
+static ssize_t fault_stacktrace_depth_store(struct config_item *item, const char *page,
+		size_t count)
+{
+	int result;
+	unsigned long tmp;
+
+	result = kstrtoul(page, 0, &tmp);
+	if (result < 0)
+		return result;
+
+	to_fault_config(item)->attr.stacktrace_depth =
+		min_t(unsigned long, tmp, MAX_STACK_TRACE_DEPTH);
+
+	return count;
+}
+
+CONFIGFS_ATTR_NAMED(fault_, stacktrace_depth, "stacktrace-depth");
+
+static ssize_t fault_xul_attr_show(unsigned long val, char *page)
+{
+	return snprintf(page, PAGE_SIZE,
+			sizeof(val) == sizeof(u32) ? "0x%08lx\n" : "0x%016lx\n", val);
+}
+
+static ssize_t fault_xul_attr_store(unsigned long *val, const char *page, size_t count)
+{
+	return fault_ulong_attr_store(val, page, count);
+}
+
+FAULT_CONFIGFS_ATTR_NAMED(require_start, "require-start", require_start, xul);
+FAULT_CONFIGFS_ATTR_NAMED(require_end, "require-end", require_end, xul);
+FAULT_CONFIGFS_ATTR_NAMED(reject_start, "reject-start", reject_start, xul);
+FAULT_CONFIGFS_ATTR_NAMED(reject_end, "reject-end", reject_end, xul);
+
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+
+static struct configfs_attribute *fault_config_attrs[] = {
+	&fault_attr_probability,
+	&fault_attr_interval,
+	&fault_attr_times,
+	&fault_attr_space,
+	&fault_attr_verbose,
+	&fault_attr_ratelimit_interval,
+	&fault_attr_ratelimit_burst,
+	&fault_attr_task_filter,
+#ifdef CONFIG_FAULT_INJECTION_STACKTRACE_FILTER
+	&fault_attr_stacktrace_depth,
+	&fault_attr_require_start,
+	&fault_attr_require_end,
+	&fault_attr_reject_start,
+	&fault_attr_reject_end,
+#endif /* CONFIG_FAULT_INJECTION_STACKTRACE_FILTER */
+	NULL,
+};
+
+static const struct config_item_type fault_config_type = {
+	.ct_attrs	= fault_config_attrs,
+	.ct_owner	= THIS_MODULE,
+};
+
+void fault_config_init(struct fault_config *config, const char *name)
+{
+	prandom_init_once(&fault_rnd_state);
+
+	config_group_init_type_name(&config->group, name, &fault_config_type);
+}
+EXPORT_SYMBOL_GPL(fault_config_init);
+
+#endif /* CONFIG_FAULT_INJECTION_CONFIGFS */