security/integrity/ima/ima_fs.c - linux - Git at Google

 /*
  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
  *
  * Authors:
  * Kylene Hall <kjhall@us.ibm.com>
  * Reiner Sailer <sailer@us.ibm.com>
  * Mimi Zohar <zohar@us.ibm.com>
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License as
  * published by the Free Software Foundation, version 2 of the
  * License.
  *
  * File: ima_fs.c
  *	implemenents security file system for reporting
  *	current measurement list and IMA statistics
  */
 #include <linux/fcntl.h>
 #include <linux/slab.h>
 #include <linux/module.h>
 #include <linux/seq_file.h>
 #include <linux/rculist.h>
 #include <linux/rcupdate.h>
 #include <linux/parser.h>
 #include <linux/vmalloc.h>

 #include "ima.h"

 static DEFINE_MUTEX(ima_write_mutex);

 bool ima_canonical_fmt;
 static int __init default_canonical_fmt_setup(char *str)
 {
 #ifdef __BIG_ENDIAN
 	ima_canonical_fmt = true;
 #endif
 	return 1;
 }
 __setup("ima_canonical_fmt", default_canonical_fmt_setup);

 static int valid_policy = 1;
 #define TMPBUFLEN 12
 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
 				     loff_t *ppos, atomic_long_t *val)
 {
 	char tmpbuf[TMPBUFLEN];
 	ssize_t len;

 	len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
 	return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
 }

 static ssize_t ima_show_htable_violations(struct file *filp,
 					  char __user *buf,
 					  size_t count, loff_t *ppos)
 {
 	return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
 }

 static const struct file_operations ima_htable_violations_ops = {
 	.read = ima_show_htable_violations,
 	.llseek = generic_file_llseek,
 };

 static ssize_t ima_show_measurements_count(struct file *filp,
 					   char __user *buf,
 					   size_t count, loff_t *ppos)
 {
 	return ima_show_htable_value(buf, count, ppos, &ima_htable.len);

 }

 static const struct file_operations ima_measurements_count_ops = {
 	.read = ima_show_measurements_count,
 	.llseek = generic_file_llseek,
 };

 /* returns pointer to hlist_node */
 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
 {
 	loff_t l = *pos;
 	struct ima_queue_entry *qe;

 	/* we need a lock since pos could point beyond last element */
 	rcu_read_lock();
 	list_for_each_entry_rcu(qe, &ima_measurements, later) {
 		if (!l--) {
 			rcu_read_unlock();
 			return qe;
 		}
 	}
 	rcu_read_unlock();
 	return NULL;
 }

 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
 {
 	struct ima_queue_entry *qe = v;

 	/* lock protects when reading beyond last element
 	 * against concurrent list-extension
 	 */
 	rcu_read_lock();
 	qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
 	rcu_read_unlock();
 	(*pos)++;

 	return (&qe->later == &ima_measurements) ? NULL : qe;
 }

 static void ima_measurements_stop(struct seq_file *m, void *v)
 {
 }

 void ima_putc(struct seq_file *m, void *data, int datalen)
 {
 	while (datalen--)
 		seq_putc(m, *(char *)data++);
 }

 /* print format:
  *       32bit-le=pcr#
  *       char[20]=template digest
  *       32bit-le=template name size
  *       char[n]=template name
  *       [eventdata length]
  *       eventdata[n]=template specific data
  */
 int ima_measurements_show(struct seq_file *m, void *v)
 {
 	/* the list never shrinks, so we don't need a lock here */
 	struct ima_queue_entry *qe = v;
 	struct ima_template_entry *e;
 	char *template_name;
 	u32 pcr, namelen, template_data_len; /* temporary fields */
 	bool is_ima_template = false;
 	int i;

 	/* get entry */
 	e = qe->entry;
 	if (e == NULL)
 		return -1;

 	template_name = (e->template_desc->name[0] != '\0') ?
 	    e->template_desc->name : e->template_desc->fmt;

 	/*
 	 * 1st: PCRIndex
 	 * PCR used defaults to the same (config option) in
 	 * little-endian format, unless set in policy
 	 */
 	pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
 	ima_putc(m, &pcr, sizeof(e->pcr));

 	/* 2nd: template digest */
 	ima_putc(m, e->digest, TPM_DIGEST_SIZE);

 	/* 3rd: template name size */
 	namelen = !ima_canonical_fmt ? strlen(template_name) :
 		cpu_to_le32(strlen(template_name));
 	ima_putc(m, &namelen, sizeof(namelen));

 	/* 4th:  template name */
 	ima_putc(m, template_name, strlen(template_name));

 	/* 5th:  template length (except for 'ima' template) */
 	if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 		is_ima_template = true;

 	if (!is_ima_template) {
 		template_data_len = !ima_canonical_fmt ? e->template_data_len :
 			cpu_to_le32(e->template_data_len);
 		ima_putc(m, &template_data_len, sizeof(e->template_data_len));
 	}

 	/* 6th:  template specific data */
 	for (i = 0; i < e->template_desc->num_fields; i++) {
 		enum ima_show_type show = IMA_SHOW_BINARY;
 		struct ima_template_field *field = e->template_desc->fields[i];

 		if (is_ima_template && strcmp(field->field_id, "d") == 0)
 			show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 		if (is_ima_template && strcmp(field->field_id, "n") == 0)
 			show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 		field->field_show(m, show, &e->template_data[i]);
 	}
 	return 0;
 }

 static const struct seq_operations ima_measurments_seqops = {
 	.start = ima_measurements_start,
 	.next = ima_measurements_next,
 	.stop = ima_measurements_stop,
 	.show = ima_measurements_show
 };

 static int ima_measurements_open(struct inode *inode, struct file *file)
 {
 	return seq_open(file, &ima_measurments_seqops);
 }

 static const struct file_operations ima_measurements_ops = {
 	.open = ima_measurements_open,
 	.read = seq_read,
 	.llseek = seq_lseek,
 	.release = seq_release,
 };

 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 {
 	u32 i;

 	for (i = 0; i < size; i++)
 		seq_printf(m, "%02x", *(digest + i));
 }

 /* print in ascii */
 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 {
 	/* the list never shrinks, so we don't need a lock here */
 	struct ima_queue_entry *qe = v;
 	struct ima_template_entry *e;
 	char *template_name;
 	int i;

 	/* get entry */
 	e = qe->entry;
 	if (e == NULL)
 		return -1;

 	template_name = (e->template_desc->name[0] != '\0') ?
 	    e->template_desc->name : e->template_desc->fmt;

 	/* 1st: PCR used (config option) */
 	seq_printf(m, "%2d ", e->pcr);

 	/* 2nd: SHA1 template hash */
 	ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);

 	/* 3th:  template name */
 	seq_printf(m, " %s", template_name);

 	/* 4th:  template specific data */
 	for (i = 0; i < e->template_desc->num_fields; i++) {
 		seq_puts(m, " ");
 		if (e->template_data[i].len == 0)
 			continue;

 		e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 							&e->template_data[i]);
 	}
 	seq_puts(m, "\n");
 	return 0;
 }

 static const struct seq_operations ima_ascii_measurements_seqops = {
 	.start = ima_measurements_start,
 	.next = ima_measurements_next,
 	.stop = ima_measurements_stop,
 	.show = ima_ascii_measurements_show
 };

 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 {
 	return seq_open(file, &ima_ascii_measurements_seqops);
 }

 static const struct file_operations ima_ascii_measurements_ops = {
 	.open = ima_ascii_measurements_open,
 	.read = seq_read,
 	.llseek = seq_lseek,
 	.release = seq_release,
 };

 static ssize_t ima_read_policy(char *path)
 {
 	void *data;
 	char *datap;
 	loff_t size;
 	int rc, pathlen = strlen(path);

 	char *p;

 	/* remove \n */
 	datap = path;
 	strsep(&datap, "\n");

 	rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
 	if (rc < 0) {
 		pr_err("Unable to open file: %s (%d)", path, rc);
 		return rc;
 	}

 	datap = data;
 	while (size > 0 && (p = strsep(&datap, "\n"))) {
 		pr_debug("rule: %s\n", p);
 		rc = ima_parse_add_rule(p);
 		if (rc < 0)
 			break;
 		size -= rc;
 	}

 	vfree(data);
 	if (rc < 0)
 		return rc;
 	else if (size)
 		return -EINVAL;
 	else
 		return pathlen;
 }

 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 				size_t datalen, loff_t *ppos)
 {
 	char *data;
 	ssize_t result;

 	if (datalen >= PAGE_SIZE)
 		datalen = PAGE_SIZE - 1;

 	/* No partial writes. */
 	result = -EINVAL;
 	if (*ppos != 0)
 		goto out;

 	data = memdup_user_nul(buf, datalen);
 	if (IS_ERR(data)) {
 		result = PTR_ERR(data);
 		goto out;
 	}

 	result = mutex_lock_interruptible(&ima_write_mutex);
 	if (result < 0)
 		goto out_free;

 	if (data[0] == '/') {
 		result = ima_read_policy(data);
 	} else if (ima_appraise & IMA_APPRAISE_POLICY) {
 		pr_err("IMA: signed policy file (specified as an absolute pathname) required\n");
 		integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 				    "policy_update", "signed policy required",
 				    1, 0);
 		if (ima_appraise & IMA_APPRAISE_ENFORCE)
 			result = -EACCES;
 	} else {
 		result = ima_parse_add_rule(data);
 	}
 	mutex_unlock(&ima_write_mutex);
 out_free:
 	kfree(data);
 out:
 	if (result < 0)
 		valid_policy = 0;

 	return result;
 }

 static struct dentry *ima_dir;
 static struct dentry *binary_runtime_measurements;
 static struct dentry *ascii_runtime_measurements;
 static struct dentry *runtime_measurements_count;
 static struct dentry *violations;
 static struct dentry *ima_policy;

 enum ima_fs_flags {
 	IMA_FS_BUSY,
 };

 static unsigned long ima_fs_flags;

 #ifdef	CONFIG_IMA_READ_POLICY
 static const struct seq_operations ima_policy_seqops = {
 		.start = ima_policy_start,
 		.next = ima_policy_next,
 		.stop = ima_policy_stop,
 		.show = ima_policy_show,
 };
 #endif

 /*
  * ima_open_policy: sequentialize access to the policy file
  */
 static int ima_open_policy(struct inode *inode, struct file *filp)
 {
 	if (!(filp->f_flags & O_WRONLY)) {
 #ifndef	CONFIG_IMA_READ_POLICY
 		return -EACCES;
 #else
 		if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 			return -EACCES;
 		if (!capable(CAP_SYS_ADMIN))
 			return -EPERM;
 		return seq_open(filp, &ima_policy_seqops);
 #endif
 	}
 	if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 		return -EBUSY;
 	return 0;
 }

 /*
  * ima_release_policy - start using the new measure policy rules.
  *
  * Initially, ima_measure points to the default policy rules, now
  * point to the new policy rules, and remove the securityfs policy file,
  * assuming a valid policy.
  */
 static int ima_release_policy(struct inode *inode, struct file *file)
 {
 	const char *cause = valid_policy ? "completed" : "failed";

 	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 		return seq_release(inode, file);

 	if (valid_policy && ima_check_policy() < 0) {
 		cause = "failed";
 		valid_policy = 0;
 	}

 	pr_info("IMA: policy update %s\n", cause);
 	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 			    "policy_update", cause, !valid_policy, 0);

 	if (!valid_policy) {
 		ima_delete_rules();
 		valid_policy = 1;
 		clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 		return 0;
 	}

 	ima_update_policy();
 #if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
 	securityfs_remove(ima_policy);
 	ima_policy = NULL;
 #elif defined(CONFIG_IMA_WRITE_POLICY)
 	clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 #endif
 	return 0;
 }

 static const struct file_operations ima_measure_policy_ops = {
 	.open = ima_open_policy,
 	.write = ima_write_policy,
 	.read = seq_read,
 	.release = ima_release_policy,
 	.llseek = generic_file_llseek,
 };

 int __init ima_fs_init(void)
 {
 	ima_dir = securityfs_create_dir("ima", NULL);
 	if (IS_ERR(ima_dir))
 		return -1;

 	binary_runtime_measurements =
 	    securityfs_create_file("binary_runtime_measurements",
 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
 				   &ima_measurements_ops);
 	if (IS_ERR(binary_runtime_measurements))
 		goto out;

 	ascii_runtime_measurements =
 	    securityfs_create_file("ascii_runtime_measurements",
 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
 				   &ima_ascii_measurements_ops);
 	if (IS_ERR(ascii_runtime_measurements))
 		goto out;

 	runtime_measurements_count =
 	    securityfs_create_file("runtime_measurements_count",
 				   S_IRUSR | S_IRGRP, ima_dir, NULL,
 				   &ima_measurements_count_ops);
 	if (IS_ERR(runtime_measurements_count))
 		goto out;

 	violations =
 	    securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 				   ima_dir, NULL, &ima_htable_violations_ops);
 	if (IS_ERR(violations))
 		goto out;

 	ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 					    ima_dir, NULL,
 					    &ima_measure_policy_ops);
 	if (IS_ERR(ima_policy))
 		goto out;

 	return 0;
 out:
 	securityfs_remove(violations);
 	securityfs_remove(runtime_measurements_count);
 	securityfs_remove(ascii_runtime_measurements);
 	securityfs_remove(binary_runtime_measurements);
 	securityfs_remove(ima_dir);
 	securityfs_remove(ima_policy);
 	return -1;
 }
	/*
	* Copyright (C) 2005,2006,2007,2008 IBM Corporation
	*
	* Authors:
	* Kylene Hall <kjhall@us.ibm.com>
	* Reiner Sailer <sailer@us.ibm.com>
	* Mimi Zohar <zohar@us.ibm.com>
	*
	* This program is free software; you can redistribute it and/or
	* modify it under the terms of the GNU General Public License as
	* published by the Free Software Foundation, version 2 of the
	* License.
	*
	* File: ima_fs.c
	* implemenents security file system for reporting
	* current measurement list and IMA statistics
	*/
	#include <linux/fcntl.h>
	#include <linux/slab.h>
	#include <linux/module.h>
	#include <linux/seq_file.h>
	#include <linux/rculist.h>
	#include <linux/rcupdate.h>
	#include <linux/parser.h>
	#include <linux/vmalloc.h>

	#include "ima.h"

	static DEFINE_MUTEX(ima_write_mutex);

	bool ima_canonical_fmt;
	static int __init default_canonical_fmt_setup(char *str)
	{
	#ifdef __BIG_ENDIAN
	ima_canonical_fmt = true;
	#endif
	return 1;
	}
	__setup("ima_canonical_fmt", default_canonical_fmt_setup);

	static int valid_policy = 1;
	#define TMPBUFLEN 12
	static ssize_t ima_show_htable_value(char __user *buf, size_t count,
	loff_t ppos, atomic_long_t val)
	{
	char tmpbuf[TMPBUFLEN];
	ssize_t len;

	len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
	return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
	}

	static ssize_t ima_show_htable_violations(struct file *filp,
	char __user *buf,
	size_t count, loff_t *ppos)
	{
	return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
	}

	static const struct file_operations ima_htable_violations_ops = {
	.read = ima_show_htable_violations,
	.llseek = generic_file_llseek,
	};

	static ssize_t ima_show_measurements_count(struct file *filp,
	char __user *buf,
	size_t count, loff_t *ppos)
	{
	return ima_show_htable_value(buf, count, ppos, &ima_htable.len);

	}

	static const struct file_operations ima_measurements_count_ops = {
	.read = ima_show_measurements_count,
	.llseek = generic_file_llseek,
	};

	/* returns pointer to hlist_node */
	static void ima_measurements_start(struct seq_file m, loff_t *pos)
	{
	loff_t l = *pos;
	struct ima_queue_entry *qe;

	/* we need a lock since pos could point beyond last element */
	rcu_read_lock();
	list_for_each_entry_rcu(qe, &ima_measurements, later) {
	if (!l--) {
	rcu_read_unlock();
	return qe;
	}
	}
	rcu_read_unlock();
	return NULL;
	}

	static void ima_measurements_next(struct seq_file m, void v, loff_t pos)
	{
	struct ima_queue_entry *qe = v;

	/* lock protects when reading beyond last element
	* against concurrent list-extension
	*/
	rcu_read_lock();
	qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
	rcu_read_unlock();
	(*pos)++;

	return (&qe->later == &ima_measurements) ? NULL : qe;
	}

	static void ima_measurements_stop(struct seq_file m, void v)
	{
	}

	void ima_putc(struct seq_file m, void data, int datalen)
	{
	while (datalen--)
	seq_putc(m, (char )data++);
	}

	/* print format:
	* 32bit-le=pcr#
	* char[20]=template digest
	* 32bit-le=template name size
	* char[n]=template name
	* [eventdata length]
	* eventdata[n]=template specific data
	*/
	int ima_measurements_show(struct seq_file m, void v)
	{
	/* the list never shrinks, so we don't need a lock here */
	struct ima_queue_entry *qe = v;
	struct ima_template_entry *e;
	char *template_name;
	u32 pcr, namelen, template_data_len; /* temporary fields */
	bool is_ima_template = false;
	int i;

	/* get entry */
	e = qe->entry;
	if (e == NULL)
	return -1;

	template_name = (e->template_desc->name[0] != '\0') ?
	e->template_desc->name : e->template_desc->fmt;

	/*
	* 1st: PCRIndex
	* PCR used defaults to the same (config option) in
	* little-endian format, unless set in policy
	*/
	pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
	ima_putc(m, &pcr, sizeof(e->pcr));

	/* 2nd: template digest */
	ima_putc(m, e->digest, TPM_DIGEST_SIZE);

	/* 3rd: template name size */
	namelen = !ima_canonical_fmt ? strlen(template_name) :
	cpu_to_le32(strlen(template_name));
	ima_putc(m, &namelen, sizeof(namelen));

	/* 4th: template name */
	ima_putc(m, template_name, strlen(template_name));

	/* 5th: template length (except for 'ima' template) */
	if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
	is_ima_template = true;

	if (!is_ima_template) {
	template_data_len = !ima_canonical_fmt ? e->template_data_len :
	cpu_to_le32(e->template_data_len);
	ima_putc(m, &template_data_len, sizeof(e->template_data_len));
	}

	/* 6th: template specific data */
	for (i = 0; i < e->template_desc->num_fields; i++) {
	enum ima_show_type show = IMA_SHOW_BINARY;
	struct ima_template_field *field = e->template_desc->fields[i];

	if (is_ima_template && strcmp(field->field_id, "d") == 0)
	show = IMA_SHOW_BINARY_NO_FIELD_LEN;
	if (is_ima_template && strcmp(field->field_id, "n") == 0)
	show = IMA_SHOW_BINARY_OLD_STRING_FMT;
	field->field_show(m, show, &e->template_data[i]);
	}
	return 0;
	}

	static const struct seq_operations ima_measurments_seqops = {
	.start = ima_measurements_start,
	.next = ima_measurements_next,
	.stop = ima_measurements_stop,
	.show = ima_measurements_show
	};

	static int ima_measurements_open(struct inode inode, struct file file)
	{
	return seq_open(file, &ima_measurments_seqops);
	}

	static const struct file_operations ima_measurements_ops = {
	.open = ima_measurements_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release,
	};

	void ima_print_digest(struct seq_file m, u8 digest, u32 size)
	{
	u32 i;

	for (i = 0; i < size; i++)
	seq_printf(m, "%02x", *(digest + i));
	}

	/* print in ascii */
	static int ima_ascii_measurements_show(struct seq_file m, void v)
	{
	/* the list never shrinks, so we don't need a lock here */
	struct ima_queue_entry *qe = v;
	struct ima_template_entry *e;
	char *template_name;
	int i;

	/* get entry */
	e = qe->entry;
	if (e == NULL)
	return -1;

	template_name = (e->template_desc->name[0] != '\0') ?
	e->template_desc->name : e->template_desc->fmt;

	/* 1st: PCR used (config option) */
	seq_printf(m, "%2d ", e->pcr);

	/* 2nd: SHA1 template hash */
	ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);

	/* 3th: template name */
	seq_printf(m, " %s", template_name);

	/* 4th: template specific data */
	for (i = 0; i < e->template_desc->num_fields; i++) {
	seq_puts(m, " ");
	if (e->template_data[i].len == 0)
	continue;

	e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
	&e->template_data[i]);
	}
	seq_puts(m, "\n");
	return 0;
	}

	static const struct seq_operations ima_ascii_measurements_seqops = {
	.start = ima_measurements_start,
	.next = ima_measurements_next,
	.stop = ima_measurements_stop,
	.show = ima_ascii_measurements_show
	};

	static int ima_ascii_measurements_open(struct inode inode, struct file file)
	{
	return seq_open(file, &ima_ascii_measurements_seqops);
	}

	static const struct file_operations ima_ascii_measurements_ops = {
	.open = ima_ascii_measurements_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = seq_release,
	};

	static ssize_t ima_read_policy(char *path)
	{
	void *data;
	char *datap;
	loff_t size;
	int rc, pathlen = strlen(path);

	char *p;

	/* remove \n */
	datap = path;
	strsep(&datap, "\n");

	rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
	if (rc < 0) {
	pr_err("Unable to open file: %s (%d)", path, rc);
	return rc;
	}

	datap = data;
	while (size > 0 && (p = strsep(&datap, "\n"))) {
	pr_debug("rule: %s\n", p);
	rc = ima_parse_add_rule(p);
	if (rc < 0)
	break;
	size -= rc;
	}

	vfree(data);
	if (rc < 0)
	return rc;
	else if (size)
	return -EINVAL;
	else
	return pathlen;
	}

	static ssize_t ima_write_policy(struct file file, const char __user buf,
	size_t datalen, loff_t *ppos)
	{
	char *data;
	ssize_t result;

	if (datalen >= PAGE_SIZE)
	datalen = PAGE_SIZE - 1;

	/* No partial writes. */
	result = -EINVAL;
	if (*ppos != 0)
	goto out;

	data = memdup_user_nul(buf, datalen);
	if (IS_ERR(data)) {
	result = PTR_ERR(data);
	goto out;
	}

	result = mutex_lock_interruptible(&ima_write_mutex);
	if (result < 0)
	goto out_free;

	if (data[0] == '/') {
	result = ima_read_policy(data);
	} else if (ima_appraise & IMA_APPRAISE_POLICY) {
	pr_err("IMA: signed policy file (specified as an absolute pathname) required\n");
	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
	"policy_update", "signed policy required",
	1, 0);
	if (ima_appraise & IMA_APPRAISE_ENFORCE)
	result = -EACCES;
	} else {
	result = ima_parse_add_rule(data);
	}
	mutex_unlock(&ima_write_mutex);
	out_free:
	kfree(data);
	out:
	if (result < 0)
	valid_policy = 0;

	return result;
	}

	static struct dentry *ima_dir;
	static struct dentry *binary_runtime_measurements;
	static struct dentry *ascii_runtime_measurements;
	static struct dentry *runtime_measurements_count;
	static struct dentry *violations;
	static struct dentry *ima_policy;

	enum ima_fs_flags {
	IMA_FS_BUSY,
	};

	static unsigned long ima_fs_flags;

	#ifdef CONFIG_IMA_READ_POLICY
	static const struct seq_operations ima_policy_seqops = {
	.start = ima_policy_start,
	.next = ima_policy_next,
	.stop = ima_policy_stop,
	.show = ima_policy_show,
	};
	#endif

	/*
	* ima_open_policy: sequentialize access to the policy file
	*/
	static int ima_open_policy(struct inode inode, struct file filp)
	{
	if (!(filp->f_flags & O_WRONLY)) {
	#ifndef CONFIG_IMA_READ_POLICY
	return -EACCES;
	#else
	if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
	return -EACCES;
	if (!capable(CAP_SYS_ADMIN))
	return -EPERM;
	return seq_open(filp, &ima_policy_seqops);
	#endif
	}
	if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
	return -EBUSY;
	return 0;
	}

	/*
	* ima_release_policy - start using the new measure policy rules.
	*
	* Initially, ima_measure points to the default policy rules, now
	* point to the new policy rules, and remove the securityfs policy file,
	* assuming a valid policy.
	*/
	static int ima_release_policy(struct inode inode, struct file file)
	{
	const char *cause = valid_policy ? "completed" : "failed";

	if ((file->f_flags & O_ACCMODE) == O_RDONLY)
	return seq_release(inode, file);

	if (valid_policy && ima_check_policy() < 0) {
	cause = "failed";
	valid_policy = 0;
	}

	pr_info("IMA: policy update %s\n", cause);
	integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
	"policy_update", cause, !valid_policy, 0);

	if (!valid_policy) {
	ima_delete_rules();
	valid_policy = 1;
	clear_bit(IMA_FS_BUSY, &ima_fs_flags);
	return 0;
	}

	ima_update_policy();
	#if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
	securityfs_remove(ima_policy);
	ima_policy = NULL;
	#elif defined(CONFIG_IMA_WRITE_POLICY)
	clear_bit(IMA_FS_BUSY, &ima_fs_flags);
	#endif
	return 0;
	}

	static const struct file_operations ima_measure_policy_ops = {
	.open = ima_open_policy,
	.write = ima_write_policy,
	.read = seq_read,
	.release = ima_release_policy,
	.llseek = generic_file_llseek,
	};

	int __init ima_fs_init(void)
	{
	ima_dir = securityfs_create_dir("ima", NULL);
	if (IS_ERR(ima_dir))
	return -1;

	binary_runtime_measurements =
	securityfs_create_file("binary_runtime_measurements",
	S_IRUSR \| S_IRGRP, ima_dir, NULL,
	&ima_measurements_ops);
	if (IS_ERR(binary_runtime_measurements))
	goto out;

	ascii_runtime_measurements =
	securityfs_create_file("ascii_runtime_measurements",
	S_IRUSR \| S_IRGRP, ima_dir, NULL,
	&ima_ascii_measurements_ops);
	if (IS_ERR(ascii_runtime_measurements))
	goto out;

	runtime_measurements_count =
	securityfs_create_file("runtime_measurements_count",
	S_IRUSR \| S_IRGRP, ima_dir, NULL,
	&ima_measurements_count_ops);
	if (IS_ERR(runtime_measurements_count))
	goto out;

	violations =
	securityfs_create_file("violations", S_IRUSR \| S_IRGRP,
	ima_dir, NULL, &ima_htable_violations_ops);
	if (IS_ERR(violations))
	goto out;

	ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
	ima_dir, NULL,
	&ima_measure_policy_ops);
	if (IS_ERR(ima_policy))
	goto out;

	return 0;
	out:
	securityfs_remove(violations);
	securityfs_remove(runtime_measurements_count);
	securityfs_remove(ascii_runtime_measurements);
	securityfs_remove(binary_runtime_measurements);
	securityfs_remove(ima_dir);
	securityfs_remove(ima_policy);
	return -1;
	}