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, 131 insertions, 0 deletions

diff --git a/lib/dump_stack.c b/lib/dump_stack.c
new file mode 100644
index 000000000..f0c78b5b5
--- /dev/null
+++ b/lib/dump_stack.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Provide a default dump_stack() function for architectures
+ * which don't implement their own.
+ */
+
+#include <linux/kernel.h>
+#include <linux/buildid.h>
+#include <linux/export.h>
+#include <linux/sched.h>
+#include <linux/sched/debug.h>
+#include <linux/smp.h>
+#include <linux/atomic.h>
+#include <linux/kexec.h>
+#include <linux/utsname.h>
+#include <linux/stop_machine.h>
+
+static char dump_stack_arch_desc_str[128];
+
+/**
+ * dump_stack_set_arch_desc - set arch-specific str to show with task dumps
+ * @fmt: printf-style format string
+ * @...: arguments for the format string
+ *
+ * The configured string will be printed right after utsname during task
+ * dumps.  Usually used to add arch-specific system identifiers.  If an
+ * arch wants to make use of such an ID string, it should initialize this
+ * as soon as possible during boot.
+ */
+void __init dump_stack_set_arch_desc(const char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	vsnprintf(dump_stack_arch_desc_str, sizeof(dump_stack_arch_desc_str),
+		  fmt, args);
+	va_end(args);
+}
+
+#if IS_ENABLED(CONFIG_STACKTRACE_BUILD_ID)
+#define BUILD_ID_FMT " %20phN"
+#define BUILD_ID_VAL vmlinux_build_id
+#else
+#define BUILD_ID_FMT "%s"
+#define BUILD_ID_VAL ""
+#endif
+
+/**
+ * dump_stack_print_info - print generic debug info for dump_stack()
+ * @log_lvl: log level
+ *
+ * Arch-specific dump_stack() implementations can use this function to
+ * print out the same debug information as the generic dump_stack().
+ */
+void dump_stack_print_info(const char *log_lvl)
+{
+	printk("%sCPU: %d UID: %u PID: %d Comm: %.20s %s%s %s %.*s %s " BUILD_ID_FMT "\n",
+	       log_lvl, raw_smp_processor_id(),
+	       __kuid_val(current_real_cred()->euid),
+	       current->pid, current->comm,
+	       kexec_crash_loaded() ? "Kdump: loaded " : "",
+	       print_tainted(),
+	       init_utsname()->release,
+	       (int)strcspn(init_utsname()->version, " "),
+	       init_utsname()->version, preempt_model_str(), BUILD_ID_VAL);
+
+	if (get_taint())
+		printk("%s%s\n", log_lvl, print_tainted_verbose());
+
+	if (dump_stack_arch_desc_str[0] != '\0')
+		printk("%sHardware name: %s\n",
+		       log_lvl, dump_stack_arch_desc_str);
+
+	print_worker_info(log_lvl, current);
+	print_stop_info(log_lvl, current);
+	print_scx_info(log_lvl, current);
+}
+
+/**
+ * show_regs_print_info - print generic debug info for show_regs()
+ * @log_lvl: log level
+ *
+ * show_regs() implementations can use this function to print out generic
+ * debug information.
+ */
+void show_regs_print_info(const char *log_lvl)
+{
+	dump_stack_print_info(log_lvl);
+}
+
+static void __dump_stack(const char *log_lvl)
+{
+	dump_stack_print_info(log_lvl);
+	show_stack(NULL, NULL, log_lvl);
+}
+
+/**
+ * dump_stack_lvl - dump the current task information and its stack trace
+ * @log_lvl: log level
+ *
+ * Architectures can override this implementation by implementing its own.
+ */
+asmlinkage __visible void dump_stack_lvl(const char *log_lvl)
+{
+	bool in_panic = panic_on_this_cpu();
+	unsigned long flags;
+
+	/*
+	 * Permit this cpu to perform nested stack dumps while serialising
+	 * against other CPUs, unless this CPU is in panic.
+	 *
+	 * When in panic, non-panic CPUs are not permitted to store new
+	 * printk messages so there is no need to synchronize the output.
+	 * This avoids potential deadlock in panic() if another CPU is
+	 * holding and unable to release the printk_cpu_sync.
+	 */
+	if (!in_panic)
+		printk_cpu_sync_get_irqsave(flags);
+
+	__dump_stack(log_lvl);
+
+	if (!in_panic)
+		printk_cpu_sync_put_irqrestore(flags);
+}
+EXPORT_SYMBOL(dump_stack_lvl);
+
+asmlinkage __visible void dump_stack(void)
+{
+	dump_stack_lvl(KERN_DEFAULT);
+}
+EXPORT_SYMBOL(dump_stack);