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, 192 insertions, 0 deletions

diff --git a/fs/efivarfs/inode.c b/fs/efivarfs/inode.c
new file mode 100644
index 000000000..f0d009555
--- /dev/null
+++ b/fs/efivarfs/inode.c
@@ -0,0 +1,192 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2012 Red Hat, Inc.
+ * Copyright (C) 2012 Jeremy Kerr <jeremy.kerr@canonical.com>
+ */
+
+#include <linux/efi.h>
+#include <linux/fs.h>
+#include <linux/ctype.h>
+#include <linux/kmemleak.h>
+#include <linux/slab.h>
+#include <linux/uuid.h>
+#include <linux/fileattr.h>
+
+#include "internal.h"
+
+static const struct inode_operations efivarfs_file_inode_operations;
+
+struct inode *efivarfs_get_inode(struct super_block *sb,
+				const struct inode *dir, int mode,
+				dev_t dev, bool is_removable)
+{
+	struct inode *inode = new_inode(sb);
+	struct efivarfs_fs_info *fsi = sb->s_fs_info;
+	struct efivarfs_mount_opts *opts = &fsi->mount_opts;
+
+	if (inode) {
+		inode->i_uid = opts->uid;
+		inode->i_gid = opts->gid;
+		inode->i_ino = get_next_ino();
+		inode->i_mode = mode;
+		simple_inode_init_ts(inode);
+		inode->i_flags = is_removable ? 0 : S_IMMUTABLE;
+		switch (mode & S_IFMT) {
+		case S_IFREG:
+			inode->i_op = &efivarfs_file_inode_operations;
+			inode->i_fop = &efivarfs_file_operations;
+			break;
+		case S_IFDIR:
+			inode->i_op = &efivarfs_dir_inode_operations;
+			inode->i_fop = &simple_dir_operations;
+			inc_nlink(inode);
+			break;
+		}
+	}
+	return inode;
+}
+
+/*
+ * Return true if 'str' is a valid efivarfs filename of the form,
+ *
+ *	VariableName-12345678-1234-1234-1234-1234567891bc
+ */
+static bool efivarfs_valid_name(const char *str, int len)
+{
+	const char *s = str + len - EFI_VARIABLE_GUID_LEN;
+
+	/*
+	 * We need a GUID, plus at least one letter for the variable name,
+	 * plus the '-' separator
+	 */
+	if (len < EFI_VARIABLE_GUID_LEN + 2)
+		return false;
+
+	/* GUID must be preceded by a '-' */
+	if (*(s - 1) != '-')
+		return false;
+
+	/*
+	 * Validate that 's' is of the correct format, e.g.
+	 *
+	 *	12345678-1234-1234-1234-123456789abc
+	 */
+	return uuid_is_valid(s);
+}
+
+static int efivarfs_create(struct mnt_idmap *idmap, struct inode *dir,
+			   struct dentry *dentry, umode_t mode)
+{
+	struct inode *inode = NULL;
+	struct efivar_entry *var;
+	int namelen, i = 0, err = 0;
+	bool is_removable = false;
+	efi_guid_t vendor;
+
+	if (!efivarfs_valid_name(dentry->d_name.name, dentry->d_name.len))
+		return -EINVAL;
+
+	/* length of the variable name itself: remove GUID and separator */
+	namelen = dentry->d_name.len - EFI_VARIABLE_GUID_LEN - 1;
+
+	err = guid_parse(dentry->d_name.name + namelen + 1, &vendor);
+	if (err)
+		return err;
+	if (guid_equal(&vendor, &LINUX_EFI_RANDOM_SEED_TABLE_GUID))
+		return -EPERM;
+
+	if (efivar_variable_is_removable(vendor,
+					 dentry->d_name.name, namelen))
+		is_removable = true;
+
+	inode = efivarfs_get_inode(dir->i_sb, dir, mode, 0, is_removable);
+	if (!inode)
+		return -ENOMEM;
+	var = efivar_entry(inode);
+
+	var->var.VendorGuid = vendor;
+
+	for (i = 0; i < namelen; i++)
+		var->var.VariableName[i] = dentry->d_name.name[i];
+
+	var->var.VariableName[i] = '\0';
+
+	inode->i_private = var;
+
+	d_make_persistent(dentry, inode);
+
+	return 0;
+}
+
+static int efivarfs_unlink(struct inode *dir, struct dentry *dentry)
+{
+	struct efivar_entry *var = d_inode(dentry)->i_private;
+
+	if (efivar_entry_delete(var))
+		return -EINVAL;
+
+	return simple_unlink(dir, dentry);
+};
+
+const struct inode_operations efivarfs_dir_inode_operations = {
+	.lookup = simple_lookup,
+	.unlink = efivarfs_unlink,
+	.create = efivarfs_create,
+};
+
+static int
+efivarfs_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+	unsigned int i_flags;
+	unsigned int flags = 0;
+
+	i_flags = d_inode(dentry)->i_flags;
+	if (i_flags & S_IMMUTABLE)
+		flags |= FS_IMMUTABLE_FL;
+
+	fileattr_fill_flags(fa, flags);
+
+	return 0;
+}
+
+static int
+efivarfs_fileattr_set(struct mnt_idmap *idmap,
+		      struct dentry *dentry, struct file_kattr *fa)
+{
+	unsigned int i_flags = 0;
+
+	if (fileattr_has_fsx(fa))
+		return -EOPNOTSUPP;
+
+	if (fa->flags & ~FS_IMMUTABLE_FL)
+		return -EOPNOTSUPP;
+
+	if (fa->flags & FS_IMMUTABLE_FL)
+		i_flags |= S_IMMUTABLE;
+
+	inode_set_flags(d_inode(dentry), i_flags, S_IMMUTABLE);
+
+	return 0;
+}
+
+/* copy of simple_setattr except that it doesn't do i_size updates */
+static int efivarfs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		   struct iattr *iattr)
+{
+	struct inode *inode = d_inode(dentry);
+	int error;
+
+	error = setattr_prepare(idmap, dentry, iattr);
+	if (error)
+		return error;
+
+	setattr_copy(idmap, inode, iattr);
+	mark_inode_dirty(inode);
+	return 0;
+}
+
+static const struct inode_operations efivarfs_file_inode_operations = {
+	.fileattr_get = efivarfs_fileattr_get,
+	.fileattr_set = efivarfs_fileattr_set,
+	.setattr      = efivarfs_setattr,
+};