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, 72 insertions, 0 deletions

diff --git a/drivers/eisa/virtual_root.c b/drivers/eisa/virtual_root.c
new file mode 100644
index 000000000..cd9515d9d
--- /dev/null
+++ b/drivers/eisa/virtual_root.c
@@ -0,0 +1,72 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Virtual EISA root driver.
+ * Acts as a placeholder if we don't have a proper EISA bridge.
+ *
+ * (C) 2003 Marc Zyngier <maz@wild-wind.fr.eu.org>
+ */
+
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/eisa.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/init.h>
+
+#if defined(CONFIG_EISA_VLB_PRIMING)
+#define EISA_FORCE_PROBE_DEFAULT 1
+#else
+#define EISA_FORCE_PROBE_DEFAULT 0
+#endif
+
+static int force_probe = EISA_FORCE_PROBE_DEFAULT;
+static void virtual_eisa_release (struct device *);
+
+/* The default EISA device parent (virtual root device).
+ * Now use a platform device, since that's the obvious choice. */
+
+static struct platform_device eisa_root_dev = {
+	.name = "eisa",
+	.id   = 0,
+	.dev  = {
+		.release = virtual_eisa_release,
+	},
+};
+
+static struct eisa_root_device eisa_bus_root = {
+	.dev		= &eisa_root_dev.dev,
+	.bus_base_addr	= 0,
+	.res		= &ioport_resource,
+	.slots		= EISA_MAX_SLOTS,
+	.dma_mask	= 0xffffffff,
+};
+
+static void virtual_eisa_release (struct device *dev)
+{
+	/* nothing really to do here */
+}
+
+static int __init virtual_eisa_root_init (void)
+{
+	int r;
+
+	if ((r = platform_device_register (&eisa_root_dev)))
+		return r;
+
+	eisa_bus_root.force_probe = force_probe;
+
+	dev_set_drvdata(&eisa_root_dev.dev, &eisa_bus_root);
+
+	if (eisa_root_register (&eisa_bus_root)) {
+		/* A real bridge may have been registered before
+		 * us. So quietly unregister. */
+		platform_device_unregister (&eisa_root_dev);
+		return -1;
+	}
+
+	return 0;
+}
+
+module_param (force_probe, int, 0444);
+
+device_initcall (virtual_eisa_root_init);