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, 165 insertions, 0 deletions

diff --git a/fs/jffs2/background.c b/fs/jffs2/background.c
new file mode 100644
index 000000000..bb0ee1a59
--- /dev/null
+++ b/fs/jffs2/background.c
@@ -0,0 +1,165 @@
+/*
+ * JFFS2 -- Journalling Flash File System, Version 2.
+ *
+ * Copyright © 2001-2007 Red Hat, Inc.
+ * Copyright © 2004-2010 David Woodhouse <dwmw2@infradead.org>
+ *
+ * Created by David Woodhouse <dwmw2@infradead.org>
+ *
+ * For licensing information, see the file 'LICENCE' in this directory.
+ *
+ */
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+#include <linux/kernel.h>
+#include <linux/jffs2.h>
+#include <linux/mtd/mtd.h>
+#include <linux/completion.h>
+#include <linux/sched/signal.h>
+#include <linux/freezer.h>
+#include <linux/kthread.h>
+#include "nodelist.h"
+
+
+static int jffs2_garbage_collect_thread(void *);
+
+void jffs2_garbage_collect_trigger(struct jffs2_sb_info *c)
+{
+	assert_spin_locked(&c->erase_completion_lock);
+	if (c->gc_task && jffs2_thread_should_wake(c))
+		send_sig(SIGHUP, c->gc_task, 1);
+}
+
+/* This must only ever be called when no GC thread is currently running */
+int jffs2_start_garbage_collect_thread(struct jffs2_sb_info *c)
+{
+	struct task_struct *tsk;
+	int ret = 0;
+
+	BUG_ON(c->gc_task);
+
+	init_completion(&c->gc_thread_start);
+	init_completion(&c->gc_thread_exit);
+
+	tsk = kthread_run(jffs2_garbage_collect_thread, c, "jffs2_gcd_mtd%d", c->mtd->index);
+	if (IS_ERR(tsk)) {
+		pr_warn("fork failed for JFFS2 garbage collect thread: %pe\n",
+			tsk);
+		complete(&c->gc_thread_exit);
+		ret = PTR_ERR(tsk);
+	} else {
+		/* Wait for it... */
+		jffs2_dbg(1, "Garbage collect thread is pid %d\n", tsk->pid);
+		wait_for_completion(&c->gc_thread_start);
+		ret = tsk->pid;
+	}
+
+	return ret;
+}
+
+void jffs2_stop_garbage_collect_thread(struct jffs2_sb_info *c)
+{
+	int wait = 0;
+	spin_lock(&c->erase_completion_lock);
+	if (c->gc_task) {
+		jffs2_dbg(1, "Killing GC task %d\n", c->gc_task->pid);
+		send_sig(SIGKILL, c->gc_task, 1);
+		wait = 1;
+	}
+	spin_unlock(&c->erase_completion_lock);
+	if (wait)
+		wait_for_completion(&c->gc_thread_exit);
+}
+
+static int jffs2_garbage_collect_thread(void *_c)
+{
+	struct jffs2_sb_info *c = _c;
+	sigset_t hupmask;
+
+	siginitset(&hupmask, sigmask(SIGHUP));
+	allow_signal(SIGKILL);
+	allow_signal(SIGSTOP);
+	allow_signal(SIGHUP);
+
+	c->gc_task = current;
+	complete(&c->gc_thread_start);
+
+	set_user_nice(current, 10);
+
+	set_freezable();
+	for (;;) {
+		sigprocmask(SIG_UNBLOCK, &hupmask, NULL);
+	again:
+		spin_lock(&c->erase_completion_lock);
+		if (!jffs2_thread_should_wake(c)) {
+			set_current_state (TASK_INTERRUPTIBLE);
+			spin_unlock(&c->erase_completion_lock);
+			jffs2_dbg(1, "%s(): sleeping...\n", __func__);
+			schedule();
+		} else {
+			spin_unlock(&c->erase_completion_lock);
+		}
+		/* Problem - immediately after bootup, the GCD spends a lot
+		 * of time in places like jffs2_kill_fragtree(); so much so
+		 * that userspace processes (like gdm and X) are starved
+		 * despite plenty of cond_resched()s and renicing.  Yield()
+		 * doesn't help, either (presumably because userspace and GCD
+		 * are generally competing for a higher latency resource -
+		 * disk).
+		 * This forces the GCD to slow the hell down.   Pulling an
+		 * inode in with read_inode() is much preferable to having
+		 * the GC thread get there first. */
+		schedule_timeout_interruptible(msecs_to_jiffies(50));
+
+		if (kthread_should_stop()) {
+			jffs2_dbg(1, "%s(): kthread_stop() called\n", __func__);
+			goto die;
+		}
+
+		/* Put_super will send a SIGKILL and then wait on the sem.
+		 */
+		while (signal_pending(current) || freezing(current)) {
+			unsigned long signr;
+
+			if (try_to_freeze())
+				goto again;
+
+			signr = kernel_dequeue_signal();
+
+			switch(signr) {
+			case SIGSTOP:
+				jffs2_dbg(1, "%s(): SIGSTOP received\n",
+					  __func__);
+				kernel_signal_stop();
+				break;
+
+			case SIGKILL:
+				jffs2_dbg(1, "%s(): SIGKILL received\n",
+					  __func__);
+				goto die;
+
+			case SIGHUP:
+				jffs2_dbg(1, "%s(): SIGHUP received\n",
+					  __func__);
+				break;
+			default:
+				jffs2_dbg(1, "%s(): signal %ld received\n",
+					  __func__, signr);
+			}
+		}
+		/* We don't want SIGHUP to interrupt us. STOP and KILL are OK though. */
+		sigprocmask(SIG_BLOCK, &hupmask, NULL);
+
+		jffs2_dbg(1, "%s(): pass\n", __func__);
+		if (jffs2_garbage_collect_pass(c) == -ENOSPC) {
+			pr_notice("No space for garbage collection. Aborting GC thread\n");
+			goto die;
+		}
+	}
+ die:
+	spin_lock(&c->erase_completion_lock);
+	c->gc_task = NULL;
+	spin_unlock(&c->erase_completion_lock);
+	kthread_complete_and_exit(&c->gc_thread_exit, 0);
+}