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, 232 insertions, 0 deletions

diff --git a/drivers/misc/open-dice.c b/drivers/misc/open-dice.c
new file mode 100644
index 000000000..b3cf59954
--- /dev/null
+++ b/drivers/misc/open-dice.c
@@ -0,0 +1,232 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2021 - Google LLC
+ * Author: David Brazdil <dbrazdil@google.com>
+ * Author: Song Guo <songguo@google.com>
+ *
+ * Driver for Open Profile for DICE.
+ *
+ * This driver takes ownership of a reserved memory region containing data
+ * generated by the Open Profile for DICE measured boot protocol. The memory
+ * contents are not interpreted by the kernel but can be mapped into a userspace
+ * process via a misc device. Userspace can also request a wipe of the memory.
+ *
+ * Userspace can access the data with (w/o error handling):
+ *
+ *     fd = open("/dev/open-dice0", O_RDWR);
+ *     read(fd, &size, sizeof(unsigned long));
+ *     data = mmap(NULL, size, PROT_READ, MAP_PRIVATE, fd, 0);
+ *     write(fd, NULL, 0); // wipe
+ *     close(fd);
+ */
+
+#include <linux/acpi.h>
+#include <linux/io.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/of_reserved_mem.h>
+#include <linux/platform_device.h>
+
+#define DRIVER_NAME "open-dice"
+
+struct open_dice_drvdata {
+	struct mutex lock;
+	char name[16];
+	phys_addr_t mem_base;
+	resource_size_t mem_size;
+	struct miscdevice misc;
+};
+
+static inline struct open_dice_drvdata *to_open_dice_drvdata(struct file *filp)
+{
+	return container_of(filp->private_data, struct open_dice_drvdata, misc);
+}
+
+static int open_dice_wipe(struct open_dice_drvdata *drvdata)
+{
+	void *kaddr;
+
+	mutex_lock(&drvdata->lock);
+	kaddr = devm_memremap(drvdata->misc.this_device, drvdata->mem_base,
+			      drvdata->mem_size, MEMREMAP_WC);
+	if (IS_ERR(kaddr)) {
+		mutex_unlock(&drvdata->lock);
+		return PTR_ERR(kaddr);
+	}
+
+	memset(kaddr, 0, drvdata->mem_size);
+	devm_memunmap(drvdata->misc.this_device, kaddr);
+	mutex_unlock(&drvdata->lock);
+	return 0;
+}
+
+/*
+ * Copies the size of the reserved memory region to the user-provided buffer.
+ */
+static ssize_t open_dice_read(struct file *filp, char __user *ptr, size_t len,
+			      loff_t *off)
+{
+	unsigned long val = to_open_dice_drvdata(filp)->mem_size;
+
+	return simple_read_from_buffer(ptr, len, off, &val, sizeof(val));
+}
+
+/*
+ * Triggers a wipe of the reserved memory region. The user-provided pointer
+ * is never dereferenced.
+ */
+static ssize_t open_dice_write(struct file *filp, const char __user *ptr,
+			       size_t len, loff_t *off)
+{
+	if (open_dice_wipe(to_open_dice_drvdata(filp)))
+		return -EIO;
+
+	/* Consume the input buffer. */
+	return len;
+}
+
+/*
+ * Creates a mapping of the reserved memory region in user address space.
+ */
+static int open_dice_mmap_prepare(struct vm_area_desc *desc)
+{
+	struct file *filp = desc->file;
+	struct open_dice_drvdata *drvdata = to_open_dice_drvdata(filp);
+
+	if (vma_desc_test(desc, VMA_MAYSHARE_BIT)) {
+		/* Do not allow userspace to modify the underlying data. */
+		if (vma_desc_test(desc, VMA_WRITE_BIT))
+			return -EPERM;
+		/* Ensure userspace cannot acquire VM_WRITE later. */
+		vma_desc_clear_flags(desc, VMA_MAYWRITE_BIT);
+	}
+
+	/* Create write-combine mapping so all clients observe a wipe. */
+	desc->page_prot = pgprot_writecombine(desc->page_prot);
+	vma_desc_set_flags(desc, VMA_DONTCOPY_BIT, VMA_DONTDUMP_BIT);
+	mmap_action_simple_ioremap(desc, drvdata->mem_base,
+				   drvdata->mem_size);
+	return 0;
+}
+
+static const struct file_operations open_dice_fops = {
+	.owner = THIS_MODULE,
+	.read = open_dice_read,
+	.write = open_dice_write,
+	.mmap_prepare = open_dice_mmap_prepare,
+};
+
+static int __init open_dice_probe(struct platform_device *pdev)
+{
+	static unsigned int dev_idx;
+	struct device *dev = &pdev->dev;
+	struct open_dice_drvdata *drvdata;
+	phys_addr_t mem_base;
+	resource_size_t mem_size;
+	int ret;
+
+	if (dev->of_node) {
+		struct reserved_mem *rmem = of_reserved_mem_lookup(dev->of_node);
+
+		if (!rmem) {
+			dev_err(dev, "failed to lookup reserved memory\n");
+			return -EINVAL;
+		}
+		mem_base = rmem->base;
+		mem_size = rmem->size;
+	} else if (is_acpi_node(dev->fwnode)) {
+		struct resource *res = platform_get_resource(pdev, IORESOURCE_MEM, 0);
+
+		if (!res) {
+			dev_err(dev, "failed to get MMIO resource\n");
+			return -EINVAL;
+		}
+		mem_base = res->start;
+		mem_size = resource_size(res);
+	} else {
+		dev_err(dev, "device not supported (no DT or ACPI node)\n");
+		return -EINVAL;
+	}
+
+	if (!mem_size || (mem_size > ULONG_MAX)) {
+		dev_err(dev, "invalid memory region size\n");
+		return -EINVAL;
+	}
+
+	if (!PAGE_ALIGNED(mem_base) || !PAGE_ALIGNED(mem_size)) {
+		dev_err(dev, "memory region must be page-aligned\n");
+		return -EINVAL;
+	}
+
+	drvdata = devm_kmalloc(dev, sizeof(*drvdata), GFP_KERNEL);
+	if (!drvdata)
+		return -ENOMEM;
+
+	*drvdata = (struct open_dice_drvdata){
+		.mem_base = mem_base,
+		.mem_size = mem_size,
+		.misc = (struct miscdevice){
+			.parent	= dev,
+			.name	= drvdata->name,
+			.minor	= MISC_DYNAMIC_MINOR,
+			.fops	= &open_dice_fops,
+			.mode	= 0600,
+		},
+	};
+	mutex_init(&drvdata->lock);
+
+	/* Index overflow check not needed, misc_register() will fail. */
+	snprintf(drvdata->name, sizeof(drvdata->name), DRIVER_NAME"%u", dev_idx++);
+
+	ret = misc_register(&drvdata->misc);
+	if (ret) {
+		dev_err(dev, "failed to register misc device '%s': %d\n",
+			drvdata->name, ret);
+		return ret;
+	}
+
+	platform_set_drvdata(pdev, drvdata);
+	return 0;
+}
+
+static void open_dice_remove(struct platform_device *pdev)
+{
+	struct open_dice_drvdata *drvdata = platform_get_drvdata(pdev);
+
+	misc_deregister(&drvdata->misc);
+}
+
+static const struct of_device_id open_dice_of_match[] = {
+	{ .compatible = "google,open-dice" },
+	{ }
+};
+
+static struct platform_driver open_dice_driver = {
+	.remove = open_dice_remove,
+	.driver = {
+		.name = DRIVER_NAME,
+		.of_match_table = open_dice_of_match,
+	},
+};
+
+static int __init open_dice_init(void)
+{
+	int ret = platform_driver_probe(&open_dice_driver, open_dice_probe);
+
+	/* DICE regions are optional. Succeed even with zero instances. */
+	return (ret == -ENODEV) ? 0 : ret;
+}
+
+static void __exit open_dice_exit(void)
+{
+	platform_driver_unregister(&open_dice_driver);
+}
+
+module_init(open_dice_init);
+module_exit(open_dice_exit);
+
+MODULE_DESCRIPTION("Driver for Open Profile for DICE.");
+MODULE_LICENSE("GPL v2");
+MODULE_AUTHOR("David Brazdil <dbrazdil@google.com>");
+MODULE_AUTHOR("Song Guo <songguo@google.com>");