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, 298 insertions, 0 deletions

diff --git a/block/blk-mq-sysfs.c b/block/blk-mq-sysfs.c
new file mode 100644
index 000000000..895397831
--- /dev/null
+++ b/block/blk-mq-sysfs.c
@@ -0,0 +1,298 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/backing-dev.h>
+#include <linux/bio.h>
+#include <linux/blkdev.h>
+#include <linux/mm.h>
+#include <linux/init.h>
+#include <linux/slab.h>
+#include <linux/workqueue.h>
+#include <linux/smp.h>
+
+#include "blk.h"
+#include "blk-mq.h"
+
+static void blk_mq_sysfs_release(struct kobject *kobj)
+{
+	struct blk_mq_ctxs *ctxs = container_of(kobj, struct blk_mq_ctxs, kobj);
+
+	free_percpu(ctxs->queue_ctx);
+	kfree(ctxs);
+}
+
+static void blk_mq_ctx_sysfs_release(struct kobject *kobj)
+{
+	struct blk_mq_ctx *ctx = container_of(kobj, struct blk_mq_ctx, kobj);
+
+	/* ctx->ctxs won't be released until all ctx are freed */
+	kobject_put(&ctx->ctxs->kobj);
+}
+
+static void blk_mq_hw_sysfs_release(struct kobject *kobj)
+{
+	struct blk_mq_hw_ctx *hctx = container_of(kobj, struct blk_mq_hw_ctx,
+						  kobj);
+
+	sbitmap_free(&hctx->ctx_map);
+	free_cpumask_var(hctx->cpumask);
+	kfree(hctx->ctxs);
+	kfree(hctx);
+}
+
+struct blk_mq_hw_ctx_sysfs_entry {
+	struct attribute attr;
+	ssize_t (*show)(struct blk_mq_hw_ctx *, char *);
+};
+
+static ssize_t blk_mq_hw_sysfs_show(struct kobject *kobj,
+				    struct attribute *attr, char *page)
+{
+	struct blk_mq_hw_ctx_sysfs_entry *entry;
+	struct blk_mq_hw_ctx *hctx;
+	struct request_queue *q;
+	ssize_t res;
+
+	entry = container_of_const(attr, struct blk_mq_hw_ctx_sysfs_entry, attr);
+	hctx = container_of(kobj, struct blk_mq_hw_ctx, kobj);
+	q = hctx->queue;
+
+	if (!entry->show)
+		return -EIO;
+
+	mutex_lock(&q->elevator_lock);
+	res = entry->show(hctx, page);
+	mutex_unlock(&q->elevator_lock);
+	return res;
+}
+
+static ssize_t blk_mq_hw_sysfs_nr_tags_show(struct blk_mq_hw_ctx *hctx,
+					    char *page)
+{
+	return sprintf(page, "%u\n", hctx->tags->nr_tags);
+}
+
+static ssize_t blk_mq_hw_sysfs_nr_reserved_tags_show(struct blk_mq_hw_ctx *hctx,
+						     char *page)
+{
+	return sprintf(page, "%u\n", hctx->tags->nr_reserved_tags);
+}
+
+static ssize_t blk_mq_hw_sysfs_cpus_show(struct blk_mq_hw_ctx *hctx, char *page)
+{
+	const size_t size = PAGE_SIZE - 1;
+	unsigned int i, first = 1;
+	int ret = 0, pos = 0;
+
+	for_each_cpu(i, hctx->cpumask) {
+		if (first)
+			ret = snprintf(pos + page, size - pos, "%u", i);
+		else
+			ret = snprintf(pos + page, size - pos, ", %u", i);
+
+		if (ret >= size - pos)
+			break;
+
+		first = 0;
+		pos += ret;
+	}
+
+	ret = snprintf(pos + page, size + 1 - pos, "\n");
+	return pos + ret;
+}
+
+static const struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_tags = {
+	.attr = {.name = "nr_tags", .mode = 0444 },
+	.show = blk_mq_hw_sysfs_nr_tags_show,
+};
+static const struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_nr_reserved_tags = {
+	.attr = {.name = "nr_reserved_tags", .mode = 0444 },
+	.show = blk_mq_hw_sysfs_nr_reserved_tags_show,
+};
+static const struct blk_mq_hw_ctx_sysfs_entry blk_mq_hw_sysfs_cpus = {
+	.attr = {.name = "cpu_list", .mode = 0444 },
+	.show = blk_mq_hw_sysfs_cpus_show,
+};
+
+static const struct attribute *const default_hw_ctx_attrs[] = {
+	&blk_mq_hw_sysfs_nr_tags.attr,
+	&blk_mq_hw_sysfs_nr_reserved_tags.attr,
+	&blk_mq_hw_sysfs_cpus.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(default_hw_ctx);
+
+static const struct sysfs_ops blk_mq_hw_sysfs_ops = {
+	.show	= blk_mq_hw_sysfs_show,
+};
+
+static const struct kobj_type blk_mq_ktype = {
+	.release	= blk_mq_sysfs_release,
+};
+
+static const struct kobj_type blk_mq_ctx_ktype = {
+	.release	= blk_mq_ctx_sysfs_release,
+};
+
+static const struct kobj_type blk_mq_hw_ktype = {
+	.sysfs_ops	= &blk_mq_hw_sysfs_ops,
+	.default_groups = default_hw_ctx_groups,
+	.release	= blk_mq_hw_sysfs_release,
+};
+
+static void blk_mq_unregister_hctx(struct blk_mq_hw_ctx *hctx)
+{
+	struct blk_mq_ctx *ctx;
+	int i;
+
+	if (!hctx->nr_ctx)
+		return;
+
+	hctx_for_each_ctx(hctx, ctx, i)
+		if (ctx->kobj.state_in_sysfs)
+			kobject_del(&ctx->kobj);
+
+	if (hctx->kobj.state_in_sysfs)
+		kobject_del(&hctx->kobj);
+}
+
+static int blk_mq_register_hctx(struct blk_mq_hw_ctx *hctx)
+{
+	struct request_queue *q = hctx->queue;
+	struct blk_mq_ctx *ctx;
+	int i, j, ret;
+
+	if (!hctx->nr_ctx)
+		return 0;
+
+	ret = kobject_add(&hctx->kobj, q->mq_kobj, "%u", hctx->queue_num);
+	if (ret)
+		return ret;
+
+	hctx_for_each_ctx(hctx, ctx, i) {
+		ret = kobject_add(&ctx->kobj, &hctx->kobj, "cpu%u", ctx->cpu);
+		if (ret)
+			goto out;
+	}
+
+	return 0;
+out:
+	hctx_for_each_ctx(hctx, ctx, j) {
+		if (j < i)
+			kobject_del(&ctx->kobj);
+	}
+	kobject_del(&hctx->kobj);
+	return ret;
+}
+
+void blk_mq_hctx_kobj_init(struct blk_mq_hw_ctx *hctx)
+{
+	kobject_init(&hctx->kobj, &blk_mq_hw_ktype);
+}
+
+void blk_mq_sysfs_deinit(struct request_queue *q)
+{
+	struct blk_mq_ctx *ctx;
+	int cpu;
+
+	for_each_possible_cpu(cpu) {
+		ctx = per_cpu_ptr(q->queue_ctx, cpu);
+		kobject_put(&ctx->kobj);
+	}
+	kobject_put(q->mq_kobj);
+}
+
+void blk_mq_sysfs_init(struct request_queue *q)
+{
+	struct blk_mq_ctx *ctx;
+	int cpu;
+
+	kobject_init(q->mq_kobj, &blk_mq_ktype);
+
+	for_each_possible_cpu(cpu) {
+		ctx = per_cpu_ptr(q->queue_ctx, cpu);
+
+		kobject_get(q->mq_kobj);
+		kobject_init(&ctx->kobj, &blk_mq_ctx_ktype);
+	}
+}
+
+int blk_mq_sysfs_register(struct gendisk *disk)
+{
+	struct request_queue *q = disk->queue;
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i, j;
+	int ret;
+
+	ret = kobject_add(q->mq_kobj, &disk_to_dev(disk)->kobj, "mq");
+	if (ret < 0)
+		return ret;
+
+	kobject_uevent(q->mq_kobj, KOBJ_ADD);
+
+	mutex_lock(&q->tag_set->tag_list_lock);
+	queue_for_each_hw_ctx(q, hctx, i) {
+		ret = blk_mq_register_hctx(hctx);
+		if (ret)
+			goto out_unreg;
+	}
+	mutex_unlock(&q->tag_set->tag_list_lock);
+	return 0;
+
+out_unreg:
+	queue_for_each_hw_ctx(q, hctx, j) {
+		if (j < i)
+			blk_mq_unregister_hctx(hctx);
+	}
+	mutex_unlock(&q->tag_set->tag_list_lock);
+
+	kobject_uevent(q->mq_kobj, KOBJ_REMOVE);
+	kobject_del(q->mq_kobj);
+	return ret;
+}
+
+void blk_mq_sysfs_unregister(struct gendisk *disk)
+{
+	struct request_queue *q = disk->queue;
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	mutex_lock(&q->tag_set->tag_list_lock);
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_unregister_hctx(hctx);
+	mutex_unlock(&q->tag_set->tag_list_lock);
+
+	kobject_uevent(q->mq_kobj, KOBJ_REMOVE);
+	kobject_del(q->mq_kobj);
+}
+
+void blk_mq_sysfs_unregister_hctxs(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+
+	if (!blk_queue_registered(q))
+		return;
+
+	queue_for_each_hw_ctx(q, hctx, i)
+		blk_mq_unregister_hctx(hctx);
+}
+
+int blk_mq_sysfs_register_hctxs(struct request_queue *q)
+{
+	struct blk_mq_hw_ctx *hctx;
+	unsigned long i;
+	int ret = 0;
+
+	if (!blk_queue_registered(q))
+		goto out;
+
+	queue_for_each_hw_ctx(q, hctx, i) {
+		ret = blk_mq_register_hctx(hctx);
+		if (ret)
+			break;
+	}
+
+out:
+	return ret;
+}