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, 116 insertions, 0 deletions

diff --git a/fs/proc/nommu.c b/fs/proc/nommu.c
new file mode 100644
index 000000000..c6e7ebc63
--- /dev/null
+++ b/fs/proc/nommu.c
@@ -0,0 +1,116 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* nommu.c: mmu-less memory info files
+ *
+ * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/time.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/mman.h>
+#include <linux/proc_fs.h>
+#include <linux/mm.h>
+#include <linux/mmzone.h>
+#include <linux/pagemap.h>
+#include <linux/swap.h>
+#include <linux/smp.h>
+#include <linux/seq_file.h>
+#include <linux/hugetlb.h>
+#include <linux/vmalloc.h>
+#include <asm/tlb.h>
+#include <asm/div64.h>
+#include "internal.h"
+
+/*
+ * display a single region to a sequenced file
+ */
+static int nommu_region_show(struct seq_file *m, struct vm_region *region)
+{
+	unsigned long ino = 0;
+	struct file *file;
+	dev_t dev = 0;
+	int flags;
+
+	flags = region->vm_flags;
+	file = region->vm_file;
+
+	if (file) {
+		struct inode *inode = file_inode(region->vm_file);
+		dev = inode->i_sb->s_dev;
+		ino = inode->i_ino;
+	}
+
+	seq_setwidth(m, 25 + sizeof(void *) * 6 - 1);
+	seq_printf(m,
+		   "%08lx-%08lx %c%c%c%c %08llx %02x:%02x %lu ",
+		   region->vm_start,
+		   region->vm_end,
+		   flags & VM_READ ? 'r' : '-',
+		   flags & VM_WRITE ? 'w' : '-',
+		   flags & VM_EXEC ? 'x' : '-',
+		   flags & VM_MAYSHARE ? flags & VM_SHARED ? 'S' : 's' : 'p',
+		   ((loff_t)region->vm_pgoff) << PAGE_SHIFT,
+		   MAJOR(dev), MINOR(dev), ino);
+
+	if (file) {
+		seq_pad(m, ' ');
+		seq_path(m, file_user_path(file), "");
+	}
+
+	seq_putc(m, '\n');
+	return 0;
+}
+
+/*
+ * display a list of all the REGIONs the kernel knows about
+ * - nommu kernels have a single flat list
+ */
+static int nommu_region_list_show(struct seq_file *m, void *_p)
+{
+	struct rb_node *p = _p;
+
+	return nommu_region_show(m, rb_entry(p, struct vm_region, vm_rb));
+}
+
+static void *nommu_region_list_start(struct seq_file *m, loff_t *_pos)
+{
+	struct rb_node *p;
+	loff_t pos = *_pos;
+
+	down_read(&nommu_region_sem);
+
+	for (p = rb_first(&nommu_region_tree); p; p = rb_next(p))
+		if (pos-- == 0)
+			return p;
+	return NULL;
+}
+
+static void nommu_region_list_stop(struct seq_file *m, void *v)
+{
+	up_read(&nommu_region_sem);
+}
+
+static void *nommu_region_list_next(struct seq_file *m, void *v, loff_t *pos)
+{
+	(*pos)++;
+	return rb_next((struct rb_node *) v);
+}
+
+static const struct seq_operations proc_nommu_region_list_seqop = {
+	.start	= nommu_region_list_start,
+	.next	= nommu_region_list_next,
+	.stop	= nommu_region_list_stop,
+	.show	= nommu_region_list_show
+};
+
+static int __init proc_nommu_init(void)
+{
+	proc_create_seq("maps", S_IRUGO, NULL, &proc_nommu_region_list_seqop);
+	return 0;
+}
+
+fs_initcall(proc_nommu_init);