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, 103 insertions, 0 deletions

diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
new file mode 100644
index 000000000..95050e719
--- /dev/null
+++ b/fs/gfs2/dentry.c
@@ -0,0 +1,103 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2006 Red Hat, Inc.  All rights reserved.
+ */
+
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/buffer_head.h>
+#include <linux/gfs2_ondisk.h>
+#include <linux/namei.h>
+#include <linux/crc32.h>
+
+#include "gfs2.h"
+#include "incore.h"
+#include "dir.h"
+#include "glock.h"
+#include "super.h"
+#include "util.h"
+#include "inode.h"
+
+/**
+ * gfs2_drevalidate - Check directory lookup consistency
+ * @dir: expected parent directory inode
+ * @name: expexted name
+ * @dentry: dentry to check
+ * @flags: lookup flags
+ *
+ * Check to make sure the lookup necessary to arrive at this inode from its
+ * parent is still good.
+ *
+ * Returns: 1 if the dentry is ok, 0 if it isn't
+ */
+
+static int gfs2_drevalidate(struct inode *dir, const struct qstr *name,
+			    struct dentry *dentry, unsigned int flags)
+{
+	struct gfs2_sbd *sdp = GFS2_SB(dir);
+	struct gfs2_inode *dip = GFS2_I(dir);
+	struct inode *inode;
+	struct gfs2_holder d_gh;
+	struct gfs2_inode *ip = NULL;
+	int error, valid;
+	int had_lock = 0;
+
+	if (flags & LOOKUP_RCU)
+		return -ECHILD;
+
+	inode = d_inode(dentry);
+
+	if (inode) {
+		if (is_bad_inode(inode))
+			return 0;
+		ip = GFS2_I(inode);
+	}
+
+	if (sdp->sd_lockstruct.ls_ops->lm_mount == NULL)
+		return 1;
+
+	had_lock = (gfs2_glock_is_locked_by_me(dip->i_gl) != NULL);
+	if (!had_lock) {
+		error = gfs2_glock_nq_init(dip->i_gl, LM_ST_SHARED, 0, &d_gh);
+		if (error)
+			return 0;
+	}
+
+	error = gfs2_dir_check(dir, name, ip);
+	valid = inode ? !error : (error == -ENOENT);
+
+	if (!had_lock)
+		gfs2_glock_dq_uninit(&d_gh);
+	return valid;
+}
+
+static int gfs2_dhash(const struct dentry *dentry, struct qstr *str)
+{
+	str->hash = gfs2_disk_hash(str->name, str->len);
+	return 0;
+}
+
+static int gfs2_dentry_delete(const struct dentry *dentry)
+{
+	struct gfs2_inode *ginode;
+
+	if (d_really_is_negative(dentry))
+		return 0;
+
+	ginode = GFS2_I(d_inode(dentry));
+	if (!gfs2_holder_initialized(&ginode->i_iopen_gh))
+		return 0;
+
+	if (test_bit(GLF_DEMOTE, &ginode->i_iopen_gh.gh_gl->gl_flags))
+		return 1;
+
+	return 0;
+}
+
+const struct dentry_operations gfs2_dops = {
+	.d_revalidate = gfs2_drevalidate,
+	.d_hash = gfs2_dhash,
+	.d_delete = gfs2_dentry_delete,
+};
+