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, 226 insertions, 0 deletions

diff --git a/fs/afs/mntpt.c b/fs/afs/mntpt.c
new file mode 100644
index 000000000..57c204a3c
--- /dev/null
+++ b/fs/afs/mntpt.c
@@ -0,0 +1,226 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* mountpoint management
+ *
+ * Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/fs.h>
+#include <linux/pagemap.h>
+#include <linux/mount.h>
+#include <linux/namei.h>
+#include <linux/gfp.h>
+#include <linux/fs_context.h>
+#include "internal.h"
+
+
+static struct dentry *afs_mntpt_lookup(struct inode *dir,
+				       struct dentry *dentry,
+				       unsigned int flags);
+static int afs_mntpt_open(struct inode *inode, struct file *file);
+static void afs_mntpt_expiry_timed_out(struct work_struct *work);
+
+const struct file_operations afs_mntpt_file_operations = {
+	.open		= afs_mntpt_open,
+	.llseek		= noop_llseek,
+};
+
+const struct inode_operations afs_mntpt_inode_operations = {
+	.lookup		= afs_mntpt_lookup,
+	.readlink	= afs_readlink,
+	.getattr	= afs_getattr,
+};
+
+const struct inode_operations afs_autocell_inode_operations = {
+	.getattr	= afs_getattr,
+};
+
+static LIST_HEAD(afs_vfsmounts);
+static DECLARE_DELAYED_WORK(afs_mntpt_expiry_timer, afs_mntpt_expiry_timed_out);
+
+static unsigned long afs_mntpt_expiry_timeout = 10 * 60;
+
+static const char afs_root_volume[] = "root.cell";
+
+/*
+ * no valid lookup procedure on this sort of dir
+ */
+static struct dentry *afs_mntpt_lookup(struct inode *dir,
+				       struct dentry *dentry,
+				       unsigned int flags)
+{
+	_enter("%p,%p{%pd2}", dir, dentry, dentry);
+	return ERR_PTR(-EREMOTE);
+}
+
+/*
+ * no valid open procedure on this sort of dir
+ */
+static int afs_mntpt_open(struct inode *inode, struct file *file)
+{
+	_enter("%p,%p{%pD2}", inode, file, file);
+	return -EREMOTE;
+}
+
+/*
+ * Set the parameters for the proposed superblock.
+ */
+static int afs_mntpt_set_params(struct fs_context *fc, struct dentry *mntpt)
+{
+	struct afs_fs_context *ctx = fc->fs_private;
+	struct afs_super_info *src_as = AFS_FS_S(mntpt->d_sb);
+	struct afs_vnode *vnode = AFS_FS_I(d_inode(mntpt));
+	struct afs_cell *cell;
+	const char *p;
+	int ret;
+
+	if (fc->net_ns != src_as->net_ns) {
+		put_net(fc->net_ns);
+		fc->net_ns = get_net(src_as->net_ns);
+	}
+
+	if (src_as->volume && src_as->volume->type == AFSVL_RWVOL) {
+		ctx->type = AFSVL_RWVOL;
+		ctx->force = true;
+	}
+	if (ctx->cell) {
+		afs_unuse_cell(ctx->cell, afs_cell_trace_unuse_mntpt);
+		ctx->cell = NULL;
+	}
+	if (test_bit(AFS_VNODE_PSEUDODIR, &vnode->flags)) {
+		/* if the directory is a pseudo directory, use the d_name */
+		unsigned size = mntpt->d_name.len;
+
+		if (size < 2)
+			return -ENOENT;
+
+		p = mntpt->d_name.name;
+		if (mntpt->d_name.name[0] == '.') {
+			size--;
+			p++;
+			ctx->type = AFSVL_RWVOL;
+			ctx->force = true;
+		}
+		if (size > AFS_MAXCELLNAME)
+			return -ENAMETOOLONG;
+
+		cell = afs_lookup_cell(ctx->net, p, size, NULL,
+				       AFS_LOOKUP_CELL_MOUNTPOINT,
+				       afs_cell_trace_use_lookup_mntpt);
+		if (IS_ERR(cell)) {
+			pr_err("kAFS: unable to lookup cell '%pd'\n", mntpt);
+			return PTR_ERR(cell);
+		}
+		ctx->cell = cell;
+
+		ctx->volname = afs_root_volume;
+		ctx->volnamesz = sizeof(afs_root_volume) - 1;
+	} else {
+		/* read the contents of the AFS special symlink */
+		DEFINE_DELAYED_CALL(cleanup);
+		const char *content;
+		loff_t size = i_size_read(d_inode(mntpt));
+
+		if (src_as->cell)
+			ctx->cell = afs_use_cell(src_as->cell, afs_cell_trace_use_mntpt);
+
+		if (size < 2 || size > PAGE_SIZE - 1)
+			return -EINVAL;
+
+		content = afs_get_link(mntpt, d_inode(mntpt), &cleanup);
+		if (IS_ERR(content)) {
+			do_delayed_call(&cleanup);
+			return PTR_ERR(content);
+		}
+
+		ret = -EINVAL;
+		if (content[size - 1] == '.')
+			ret = vfs_parse_fs_qstr(fc, "source",
+						&QSTR_LEN(content, size - 1));
+		do_delayed_call(&cleanup);
+		if (ret < 0)
+			return ret;
+
+		/* Don't cross a backup volume mountpoint from a backup volume */
+		if (src_as->volume && src_as->volume->type == AFSVL_BACKVOL &&
+		    ctx->type == AFSVL_BACKVOL)
+			return -ENODEV;
+	}
+
+	return 0;
+}
+
+/*
+ * create a vfsmount to be automounted
+ */
+static struct vfsmount *afs_mntpt_do_automount(struct dentry *mntpt)
+{
+	struct fs_context *fc;
+	struct vfsmount *mnt;
+	int ret;
+
+	BUG_ON(!d_inode(mntpt));
+
+	fc = fs_context_for_submount(&afs_fs_type, mntpt);
+	if (IS_ERR(fc))
+		return ERR_CAST(fc);
+
+	ret = afs_mntpt_set_params(fc, mntpt);
+	if (!ret)
+		mnt = fc_mount(fc);
+	else
+		mnt = ERR_PTR(ret);
+
+	put_fs_context(fc);
+	return mnt;
+}
+
+/*
+ * handle an automount point
+ */
+struct vfsmount *afs_d_automount(struct path *path)
+{
+	struct vfsmount *newmnt;
+
+	_enter("{%pd}", path->dentry);
+
+	newmnt = afs_mntpt_do_automount(path->dentry);
+	if (IS_ERR(newmnt))
+		return newmnt;
+
+	mnt_set_expiry(newmnt, &afs_vfsmounts);
+	queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
+			   afs_mntpt_expiry_timeout * HZ);
+	_leave(" = %p", newmnt);
+	return newmnt;
+}
+
+/*
+ * handle mountpoint expiry timer going off
+ */
+static void afs_mntpt_expiry_timed_out(struct work_struct *work)
+{
+	_enter("");
+
+	if (!list_empty(&afs_vfsmounts)) {
+		mark_mounts_for_expiry(&afs_vfsmounts);
+		queue_delayed_work(afs_wq, &afs_mntpt_expiry_timer,
+				   afs_mntpt_expiry_timeout * HZ);
+	}
+
+	_leave("");
+}
+
+/*
+ * kill the AFS mountpoint timer if it's still running
+ */
+void afs_mntpt_kill_timer(void)
+{
+	_enter("");
+
+	ASSERT(list_empty(&afs_vfsmounts));
+	cancel_delayed_work_sync(&afs_mntpt_expiry_timer);
+}