How does a lsm security module open a config file?

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phanix@hotmail.com

I am now working on a lsm module.
I want this module to open and read "/etc/myattr.conf" when initializing.
There are a lot of functions in the kernel, path_init(), path_walk(),
dentry_open(), flip_open(), kernel_read(),
Should I use them? How?

My module looks like this:
(In fact, I copy most of the open_exec() in fs/exec.c to open_conf_file() )

struct file *open_conf_file(const char *name)
{
	struct nameidata nd;
	struct inode *inode;
	struct file *file;
	int err = 0;

	if (path_init(name, LOOKUP_FOLLOW|LOOKUP_POSITIVE, &nd))
		err = path_walk(name, &nd);
	file = ERR_PTR(err);
	if (!err) {
		inode = nd.dentry->d_inode;
		file = ERR_PTR(-EACCES);
		if ( !(nd.mnt->mnt_flags & MNT_NOEXEC) && S_ISREG(inode->i_mode)) {
			int err = permission(inode, MAY_READ);
			if (!err && !(inode->i_mode & 0444))
				err = -EACCES;
			file = ERR_PTR(err);
			if (!err) {
				file = dentry_open(nd.dentry, nd.mnt, O_RDONLY);

				if (!IS_ERR(file)) {
					err = deny_write_access(file);
					if (err) {
						fput(file);
						file = ERR_PTR(err);
					}
				}

out:
				return file;
			}
		}
		path_release(&nd);
	}
	goto out;
}

static int __init mec_init (void)
{
	struct file *fd = NULL;
         ..........
         ..........

	/* register module with the security framework */

         ..........

	// first, read the config file into buf
	memset( buffer, ' ', BUF_LEN );
	if( IS_ERR( fd = open_conf_file( "/etc/myattr.conf" ) ) )
		return -EINVAL;

         ...........
	}

When insmod this module, the kernel collapse.
Please, help me.

                                                        X.H. Beijing

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