Message-ID: <255c119de8f8665b88c411d981762fddc0fe7eaa.camel@huaweicloud.com>
Subject: Re: [RFC PATCH v9 05/16] ipe: add userspace interface
From:   Roberto Sassu <roberto.sassu@huaweicloud.com>
To:     Fan Wu <wufan@linux.microsoft.com>, corbet@lwn.net,
        zohar@linux.ibm.com, jmorris@namei.org, serge@hallyn.com,
        tytso@mit.edu, ebiggers@kernel.org, axboe@kernel.dk,
        agk@redhat.com, snitzer@kernel.org, eparis@redhat.com,
        paul@paul-moore.com
Cc:     linux-doc@vger.kernel.org, linux-integrity@vger.kernel.org,
        linux-security-module@vger.kernel.org,
        linux-fscrypt@vger.kernel.org, linux-block@vger.kernel.org,
        dm-devel@redhat.com, linux-audit@redhat.com,
        roberto.sassu@huawei.com, linux-kernel@vger.kernel.org,
        Deven Bowers <deven.desai@linux.microsoft.com>
Date:   Tue, 31 Jan 2023 11:49:44 +0100
In-Reply-To: <1675119451-23180-6-git-send-email-wufan@linux.microsoft.com>
References: <1675119451-23180-1-git-send-email-wufan@linux.microsoft.com>
         <1675119451-23180-6-git-send-email-wufan@linux.microsoft.com>
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On Mon, 2023-01-30 at 14:57 -0800, Fan Wu wrote:
> From: Deven Bowers <deven.desai@linux.microsoft.com>
> 
> As is typical with LSMs, IPE uses securityfs as its interface with
> userspace. for a complete list of the interfaces and the respective
> inputs/outputs, please see the documentation under
> admin-guide/LSM/ipe.rst
> 
> Signed-off-by: Deven Bowers <deven.desai@linux.microsoft.com>
> Signed-off-by: Fan Wu <wufan@linux.microsoft.com>
> 
> ---
> v2:
>   + Split evaluation loop, access control hooks,
>     and evaluation loop from policy parser and userspace
>     interface to pass mailing list character limit
> 
> v3:
>   + Move policy load and activation audit event to 03/12
>   + Fix a potential panic when a policy failed to load.
>   + use pr_warn for a failure to parse instead of an
>     audit record
>   + Remove comments from headers
>   + Add lockdep assertions to ipe_update_active_policy and
>     ipe_activate_policy
>   + Fix up warnings with checkpatch --strict
>   + Use file_ns_capable for CAP_MAC_ADMIN for securityfs
>     nodes.
>   + Use memdup_user instead of kzalloc+simple_write_to_buffer.
>   + Remove strict_parse command line parameter, as it is added
>     by the sysctl command line.
>   + Prefix extern variables with ipe_
> 
> v4:
>   + Remove securityfs to reverse-dependency
>   + Add SHA1 reverse dependency.
>   + Add versioning scheme for IPE properties, and associated
>     interface to query the versioning scheme.
>   + Cause a parser to always return an error on unknown syntax.
>   + Remove strict_parse option
>   + Change active_policy interface from sysctl, to securityfs,
>     and change scheme.
> 
> v5:
>   + Cause an error if a default action is not defined for each
>     operaiton.
>   + Minor function renames
> 
> v6:
>   + No changes
> 
> v7:
>   + Propogating changes to support the new ipe_context structure in the
>     evaluation loop.
> 
>   + Further split the parser and userspace interface changes into
>     separate commits.
> 
>   + "raw" was renamed to "pkcs7" and made read only
>   + "raw"'s write functionality (update a policy) moved to "update"
>   + introduced "version", "policy_name" nodes.
>   + "content" renamed to "policy"
>   + changes to allow the compiled-in policy to be treated
>     identical to deployed-after-the-fact policies.
> 
> v8:
>   + Prevent securityfs initialization if the LSM is disabled
> 
> v9:
>   + Switch to securityfs_recursive_remove for policy folder deletion
> ---
>  security/ipe/Makefile    |   2 +
>  security/ipe/fs.c        | 101 +++++++++
>  security/ipe/fs.h        |  17 ++
>  security/ipe/ipe.c       |   3 +
>  security/ipe/ipe.h       |   2 +
>  security/ipe/policy.c    | 135 ++++++++++++
>  security/ipe/policy.h    |   7 +
>  security/ipe/policy_fs.c | 459 +++++++++++++++++++++++++++++++++++++++
>  8 files changed, 726 insertions(+)
>  create mode 100644 security/ipe/fs.c
>  create mode 100644 security/ipe/fs.h
>  create mode 100644 security/ipe/policy_fs.c
> 
> diff --git a/security/ipe/Makefile b/security/ipe/Makefile
> index d7f2870d7c09..8602d71250b4 100644
> --- a/security/ipe/Makefile
> +++ b/security/ipe/Makefile
> @@ -7,7 +7,9 @@
>  
>  obj-$(CONFIG_SECURITY_IPE) += \
>  	eval.o \
> +	fs.o \
>  	hooks.o \
>  	ipe.o \
>  	policy.o \
> +	policy_fs.o \
>  	policy_parser.o \
> diff --git a/security/ipe/fs.c b/security/ipe/fs.c
> new file mode 100644
> index 000000000000..9f6a4867bec2
> --- /dev/null
> +++ b/security/ipe/fs.c
> @@ -0,0 +1,101 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +#include "ipe.h"
> +#include "fs.h"
> +#include "policy.h"
> +
> +#include <linux/dcache.h>
> +#include <linux/security.h>
> +
> +static struct dentry *np __ro_after_init;
> +static struct dentry *root __ro_after_init;
> +struct dentry *policy_root __ro_after_init;
> +
> +/**
> + * new_policy - Write handler for the securityfs node, "ipe/new_policy".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Suppleis a buffer passed to the write syscall.

Typo: Suppleis.

> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t new_policy(struct file *f, const char __user *data,
> +			  size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	char *copy = NULL;
> +	struct ipe_policy *p = NULL;
> +
> +	if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
> +		return -EPERM;
> +
> +	copy = memdup_user_nul(data, len);
> +	if (IS_ERR(copy)) {
> +		rc = PTR_ERR(copy);
> +		goto err;
> +	}
> +
> +	p = ipe_new_policy(NULL, 0, copy, len);
> +	if (IS_ERR(p)) {
> +		rc = PTR_ERR(p);
> +		goto err;
> +	}
> +
> +	rc = ipe_new_policyfs_node(p);
> +	if (rc)
> +		goto err;

Uhm, don't you need to do cleanup of allocated memory or revert the
actions of ipe_new_policy()?

> +
> +err:
> +	return (rc < 0) ? rc : len;
> +}
> +
> +static const struct file_operations np_fops = {
> +	.write = new_policy,
> +};
> +
> +/**
> + * ipe_init_securityfs - Initialize IPE's securityfs tree at fsinit.
> + *
> + * Return:
> + * * !0	- Error
> + * * 0	- OK
> + */
> +static int __init ipe_init_securityfs(void)
> +{
> +	int rc = 0;
> +
> +	if (!ipe_enabled)
> +		return -EOPNOTSUPP;
> +
> +	root = securityfs_create_dir("ipe", NULL);
> +	if (IS_ERR(root)) {
> +		rc = PTR_ERR(root);
> +		goto err;
> +	}
> +
> +	np = securityfs_create_file("new_policy", 0200, root, NULL, &np_fops);
> +	if (IS_ERR(np)) {
> +		rc = PTR_ERR(np);
> +		goto err;
> +	}
> +
> +	policy_root = securityfs_create_dir("policies", root);
> +	if (IS_ERR(policy_root)) {
> +		rc = PTR_ERR(policy_root);
> +		goto err;
> +	}
> +
> +	return 0;
> +err:
> +	securityfs_remove(np);
> +	securityfs_remove(root);
> +	securityfs_remove(policy_root);
> +	return rc;
> +}
> +
> +fs_initcall(ipe_init_securityfs);
> diff --git a/security/ipe/fs.h b/security/ipe/fs.h
> new file mode 100644
> index 000000000000..fa105d9d6fc5
> --- /dev/null
> +++ b/security/ipe/fs.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +
> +#ifndef IPE_FS_H
> +#define IPE_FS_H
> +
> +#include "policy.h"
> +
> +extern struct dentry *policy_root __ro_after_init;
> +
> +void ipe_soft_del_policyfs(struct ipe_policy *p);
> +int ipe_new_policyfs_node(struct ipe_policy *p);
> +void ipe_del_policyfs_node(struct ipe_policy *p);
> +
> +#endif /* IPE_FS_H */
> diff --git a/security/ipe/ipe.c b/security/ipe/ipe.c
> index 551c6d90ac11..bef923026b50 100644
> --- a/security/ipe/ipe.c
> +++ b/security/ipe/ipe.c
> @@ -5,6 +5,8 @@
>  
>  #include "ipe.h"
>  
> +bool ipe_enabled;
> +
>  static struct lsm_blob_sizes ipe_blobs __lsm_ro_after_init = {
>  };
>  
> @@ -30,6 +32,7 @@ static int __init ipe_init(void)
>  	int rc = 0;
>  
>  	security_add_hooks(ipe_hooks, ARRAY_SIZE(ipe_hooks), "ipe");
> +	ipe_enabled = true;
>  
>  	return rc;
>  }
> diff --git a/security/ipe/ipe.h b/security/ipe/ipe.h
> index ee7ec3f3b55d..43cc132ed048 100644
> --- a/security/ipe/ipe.h
> +++ b/security/ipe/ipe.h
> @@ -10,4 +10,6 @@
>  
>  #include <linux/lsm_hooks.h>
>  
> +extern bool ipe_enabled;
> +
>  #endif /* IPE_H */
> diff --git a/security/ipe/policy.c b/security/ipe/policy.c
> index 772d876b1087..a5e9c6e5691b 100644
> --- a/security/ipe/policy.c
> +++ b/security/ipe/policy.c
> @@ -4,12 +4,39 @@
>   */
>  
>  #include "ipe.h"
> +#include "eval.h"
> +#include "fs.h"
>  #include "policy.h"
>  #include "policy_parser.h"
>  #include "digest.h"
>  
>  #include <linux/verification.h>
>  
> +/* lock for synchronizing writers across ipe policy */
> +DEFINE_SPINLOCK(ipe_policy_lock);
> +
> +/**
> + * ver_to_u64 - Convert an internal ipe_policy_version to a u64.
> + * @p: Policy to extract the version from.
> + *
> + * Bits (LSB is index 0):
> + *	[48,32] -> Major
> + *	[32,16] -> Minor
> + *	[16, 0] -> Revision
> + *
> + * Return: u64 version of the embedded version structure.
> + */
> +static inline u64 ver_to_u64(const struct ipe_policy *const p)
> +{
> +	u64 r = 0;
> +
> +	r = (((u64)p->parsed->version.major) << 32)
> +	  | (((u64)p->parsed->version.minor) << 16)
> +	  | ((u64)(p->parsed->version.rev));
> +
> +	return r;
> +}
> +
>  /**
>   * ipe_free_policy - Deallocate a given IPE policy.
>   * @p: Supplies the policy to free.
> @@ -21,6 +48,7 @@ void ipe_free_policy(struct ipe_policy *p)
>  	if (IS_ERR_OR_NULL(p))
>  		return;
>  
> +	ipe_del_policyfs_node(p);
>  	free_parsed_policy(p->parsed);
>  	if (!p->pkcs7)
>  		kfree(p->text);
> @@ -39,6 +67,70 @@ static int set_pkcs7_data(void *ctx, const void *data, size_t len,
>  	return 0;
>  }
>  
> +/**
> + * ipe_update_policy - parse a new policy and replace @old with it.
> + * @addr: Supplies a pointer to the i_private for saving policy.
> + * @text: Supplies a pointer to the plain text policy.
> + * @textlen: Supplies the length of @text.
> + * @pkcs7: Supplies a pointer to a buffer containing a pkcs7 message.
> + * @pkcs7len: Supplies the length of @pkcs7len.
> + *
> + * @text/@textlen is mutually exclusive with @pkcs7/@pkcs7len - see
> + * ipe_new_policy.
> + *
> + * Return:
> + * * !IS_ERR	- OK
> + * * -ENOENT	- Policy doesn't exist
> + * * -EINVAL	- New policy is invalid
> + */
> +struct ipe_policy *ipe_update_policy(struct ipe_policy __rcu **addr,
> +				     const char *text, size_t textlen,
> +				     const char *pkcs7, size_t pkcs7len)
> +{
> +	int rc = 0;
> +	struct ipe_policy *old, *new;
> +
> +	old = ipe_get_policy_rcu(*addr);
> +	if (!old) {
> +		rc = -ENOENT;
> +		goto err;
> +	}
> +
> +	new = ipe_new_policy(text, textlen, pkcs7, pkcs7len);
> +	if (IS_ERR(new)) {
> +		rc = PTR_ERR(new);
> +		goto err;
> +	}
> +
> +	if (strcmp(new->parsed->name, old->parsed->name)) {
> +		rc = -EINVAL;
> +		goto err;
> +	}
> +
> +	if (ver_to_u64(old) > ver_to_u64(new)) {
> +		rc = -EINVAL;
> +		goto err;
> +	}
> +
> +	if (ipe_is_policy_active(old)) {
> +		spin_lock(&ipe_policy_lock);
> +		rcu_assign_pointer(ipe_active_policy, new);
> +		spin_unlock(&ipe_policy_lock);
> +		synchronize_rcu();
> +	}
> +
> +	rcu_assign_pointer(*addr, new);
> +
> +	swap(new->policyfs, old->policyfs);
> +	ipe_free_policy(old);
> +
> +	goto out;
> +err:
> +	ipe_free_policy(new);
> +out:
> +	return (rc < 0) ? ERR_PTR(rc) : new;
> +}

I would like more to see all the functions managing the policy
together. If the patch is too long, you could further split by adding
the helpers (that don't directly deal with the policy) in a separate
patch.

Here you would simply instantiate dirs/files in securityfs and call the
existing functions previously introduced.

Roberto

> +
>  /**
>   * ipe_new_policy - Allocate and parse an ipe_policy structure.
>   *
> @@ -117,3 +209,46 @@ struct ipe_policy *ipe_get_policy_rcu(struct ipe_policy __rcu *p)
>  
>  	return rv;
>  }
> +
> +/**
> + * ipe_set_active_pol - Make @p the active policy.
> + * @p: Supplies a pointer to the policy to make active.
> + */
> +int ipe_set_active_pol(const struct ipe_policy *p)
> +{
> +	int rc = 0;
> +	struct ipe_policy *ap = NULL;
> +
> +	ap = ipe_get_policy_rcu(ipe_active_policy);
> +	if (ap && ver_to_u64(ap) > ver_to_u64(p)) {
> +		rc = -EINVAL;
> +		goto out;
> +	}
> +
> +	spin_lock(&ipe_policy_lock);
> +	rcu_assign_pointer(ipe_active_policy, p);
> +	spin_unlock(&ipe_policy_lock);
> +	synchronize_rcu();
> +
> +out:
> +	return rc;
> +}
> +
> +/**
> + * ipe_is_policy_active - Determine wehther @p is the active policy.
> + * @p: Supplies a pointer to the policy to check.
> + *
> + * Return:
> + * * true	- @p is the active policy
> + * * false	- @p is not the active policy
> + */
> +bool ipe_is_policy_active(const struct ipe_policy *p)
> +{
> +	bool rv;
> +
> +	rcu_read_lock();
> +	rv = rcu_access_pointer(ipe_active_policy) == p;
> +	rcu_read_unlock();
> +
> +	return rv;
> +}
> diff --git a/security/ipe/policy.h b/security/ipe/policy.h
> index 967d816cd5cd..0cb42b6f246e 100644
> --- a/security/ipe/policy.h
> +++ b/security/ipe/policy.h
> @@ -70,11 +70,18 @@ struct ipe_policy {
>  	size_t		textlen;
>  
>  	struct ipe_parsed_policy *parsed;
> +
> +	struct dentry *policyfs;
>  };
>  
>  struct ipe_policy *ipe_new_policy(const char *text, size_t textlen,
>  				  const char *pkcs7, size_t pkcs7len);
>  void ipe_free_policy(struct ipe_policy *pol);
>  struct ipe_policy *ipe_get_policy_rcu(struct ipe_policy __rcu *p);
> +struct ipe_policy *ipe_update_policy(struct ipe_policy **addr, const char *text,
> +				     size_t textlen, const char *pkcs7,
> +				     size_t pkcs7len);
> +int ipe_set_active_pol(const struct ipe_policy *p);
> +bool ipe_is_policy_active(const struct ipe_policy *p);
>  
>  #endif /* IPE_POLICY_H */
> diff --git a/security/ipe/policy_fs.c b/security/ipe/policy_fs.c
> new file mode 100644
> index 000000000000..72759cc8938d
> --- /dev/null
> +++ b/security/ipe/policy_fs.c
> @@ -0,0 +1,459 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright (C) Microsoft Corporation. All rights reserved.
> + */
> +#include "ipe.h"
> +#include "policy.h"
> +#include "fs.h"
> +
> +#include <linux/fs.h>
> +#include <linux/namei.h>
> +#include <linux/types.h>
> +#include <linux/dcache.h>
> +#include <linux/security.h>
> +
> +#define MAX_VERSION_SIZE ARRAY_SIZE("65535.65535.65535")
> +
> +/**
> + * find_policy - return a policy pointer saved in i_private of a dentry.
> + * @f: Securityfs object that contains a link to the dentry containing the
> + *     policy structure.
> + *
> + * Return: Always-Valid Address Pointer
> + */
> +static inline struct ipe_policy __rcu **find_policy(struct file *f)
> +{
> +	struct dentry *link;
> +
> +	link = d_inode(f->f_path.dentry)->i_private;
> +
> +	return (struct ipe_policy __rcu **)&(d_inode(link)->i_private);
> +}
> +
> +/**
> + * ipefs_file - defines a file in securityfs.
> + */
> +struct ipefs_file {
> +	const char	*name;
> +	umode_t		access;
> +	const struct	file_operations *fops;
> +};
> +
> +/**
> + * read_pkcs7 - Read handler for "ipe/policies/$name/pkcs7".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Suppleis a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * @data will be populated with the pkcs7 blob representing the policy
> + * on success. If the policy is unsigned (like the boot policy), this
> + * will return -ENOENT.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t read_pkcs7(struct file *f, char __user *data,
> +			  size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	struct ipe_policy *p = NULL;
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p)
> +		return -ENOENT;
> +
> +	if (!p->pkcs7) {
> +		rc = -ENOENT;
> +		goto out;
> +	}
> +
> +	rc = simple_read_from_buffer(data, len, offset, p->pkcs7, p->pkcs7len);
> +
> +out:
> +	return rc;
> +}
> +
> +/**
> + * read_policy - Read handler for "ipe/policies/$name/policy".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Suppleis a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * @data will be populated with the plain-text version of the policy
> + * on success.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t read_policy(struct file *f, char __user *data,
> +			   size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	struct ipe_policy *p = NULL;
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p)
> +		return -ENOENT;
> +
> +	rc = simple_read_from_buffer(data, len, offset, p->text, p->textlen);
> +
> +	return rc;
> +}
> +
> +/**
> + * read_name: Read handler for "ipe/policies/$name/name".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Suppleis a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * @data will be populated with the policy_name attribute on success.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t read_name(struct file *f, char __user *data,
> +			 size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	struct ipe_policy *p = NULL;
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p)
> +		return -ENOENT;
> +
> +	rc = simple_read_from_buffer(data, len, offset, p->parsed->name,
> +				     strlen(p->parsed->name));
> +
> +	return rc;
> +}
> +
> +/**
> + * read_version - Read handler for "ipe/policies/$name/version".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Suppleis a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * @data will be populated with the version string on success.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t read_version(struct file *f, char __user *data,
> +			    size_t len, loff_t *offset)
> +{
> +	ssize_t rc = 0;
> +	size_t bufsize = 0;
> +	struct ipe_policy *p = NULL;
> +	char buffer[MAX_VERSION_SIZE] = { 0 };
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p)
> +		return -ENOENT;
> +
> +	bufsize = scnprintf(buffer, ARRAY_SIZE(buffer), "%hu.%hu.%hu",
> +			    p->parsed->version.major, p->parsed->version.minor,
> +			    p->parsed->version.rev);
> +
> +	rc = simple_read_from_buffer(data, len, offset, buffer, bufsize);
> +
> +	return rc;
> +}
> +
> +/**
> + * setactive - Write handler for "ipe/policies/$name/active".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Supplies a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t setactive(struct file *f, const char __user *data,
> +			 size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	bool value = false;
> +	struct ipe_policy *p = NULL;
> +
> +	if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
> +		return -EPERM;
> +
> +	rc = kstrtobool_from_user(data, len, &value);
> +	if (rc)
> +		goto out;
> +
> +	if (!value) {
> +		rc = -EINVAL;
> +		goto out;
> +	}
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p) {
> +		rc = -ENOENT;
> +		goto out;
> +	}
> +
> +	rc = ipe_set_active_pol(p);
> +
> +out:
> +	return (rc < 0) ? rc : len;
> +}
> +
> +/**
> + * getactive - Read handler for "ipe/policies/$name/active".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Suppleis a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * @data will be populated with the 1 or 0 depending on if the
> + * corresponding policy is active.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t getactive(struct file *f, char __user *data,
> +			 size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	const char *str;
> +	struct ipe_policy *p = NULL;
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p) {
> +		rc = -ENOENT;
> +		goto out;
> +	}
> +
> +	str = ipe_is_policy_active(p) ? "1" : "0";
> +	rc = simple_read_from_buffer(data, len, offset, str, 1);
> +
> +out:
> +	return rc;
> +}
> +
> +/**
> + * update_policy - Write handler for "ipe/policies/$name/update".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Supplies a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * On success this updates the policy represented by $name,
> + * in-place.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t update_policy(struct file *f, const char __user *data,
> +			     size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	char *copy = NULL;
> +	struct inode *ino = NULL;
> +	struct ipe_policy *new = NULL;
> +	struct ipe_policy __rcu **addr = NULL;
> +
> +	if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
> +		return -EPERM;
> +
> +	copy = memdup_user(data, len);
> +	if (IS_ERR(copy)) {
> +		rc = PTR_ERR(copy);
> +		goto err;
> +	}
> +
> +	ino = d_inode(f->f_path.dentry->d_parent);
> +	inode_lock(ino);
> +	addr = find_policy(f);
> +	new = ipe_update_policy(addr, NULL, 0, copy, len);
> +	inode_unlock(ino);
> +	synchronize_rcu();
> +	if (IS_ERR(new)) {
> +		rc = PTR_ERR(new);
> +		goto err;
> +	}
> +
> +	kfree(copy);
> +	return len;
> +err:
> +	kfree(copy);
> +	return rc;
> +}
> +
> +/**
> + * delete_policy - write handler for  "ipe/policies/$name/delete".
> + * @f: Supplies a file structure representing the securityfs node.
> + * @data: Supplies a buffer passed to the write syscall.
> + * @len: Supplies the length of @data.
> + * @offset: unused.
> + *
> + * On success this deletes the policy represented by $name.
> + *
> + * Return:
> + * * >0	- Success, Length of buffer written
> + * * <0	- Error
> + */
> +static ssize_t delete_policy(struct file *f, const char __user *data,
> +			     size_t len, loff_t *offset)
> +{
> +	int rc = 0;
> +	bool value = false;
> +	struct ipe_policy *p = NULL;
> +
> +	if (!file_ns_capable(f, &init_user_ns, CAP_MAC_ADMIN))
> +		return -EPERM;
> +
> +	rc = kstrtobool_from_user(data, len, &value);
> +	if (rc)
> +		goto out;
> +
> +	if (!value) {
> +		rc = -EINVAL;
> +		goto out;
> +	}
> +
> +	p = ipe_get_policy_rcu(*find_policy(f));
> +	if (!p) {
> +		rc = -ENOENT;
> +		goto out;
> +	}
> +
> +	if (ipe_is_policy_active(p)) {
> +		rc = -EPERM;
> +		goto out;
> +	}
> +
> +	ipe_free_policy(p);
> +out:
> +	return (rc < 0) ? rc : len;
> +}
> +
> +static const struct file_operations content_fops = {
> +	.read = read_policy,
> +};
> +
> +static const struct file_operations pkcs7_fops = {
> +	.read = read_pkcs7,
> +};
> +
> +static const struct file_operations name_fops = {
> +	.read = read_name,
> +};
> +
> +static const struct file_operations ver_fops = {
> +	.read = read_version,
> +};
> +
> +static const struct file_operations active_fops = {
> +	.write = setactive,
> +	.read = getactive,
> +};
> +
> +static const struct file_operations update_fops = {
> +	.write = update_policy,
> +};
> +
> +static const struct file_operations delete_fops = {
> +	.write = delete_policy,
> +};
> +
> +/**
> + * policy_subdir - files under a policy subdirectory
> + */
> +static const struct ipefs_file policy_subdir[] = {
> +	{ "pkcs7", 0444, &pkcs7_fops },
> +	{ "policy", 0444, &content_fops },
> +	{ "name", 0444, &name_fops },
> +	{ "version", 0444, &ver_fops },
> +	{ "active", 0600, &active_fops },
> +	{ "update", 0200, &update_fops },
> +	{ "delete", 0200, &delete_fops },
> +};
> +
> +/**
> + * soft_del_policyfs - soft delete a policyfs node.
> + * @p: Supplies a ipe_policy associated with the node to delete.
> + *
> + * This deletes the i_private field of a policyfs node.
> + */
> +static void soft_del_policyfs(struct ipe_policy *p)
> +{
> +	struct inode *ino = NULL;
> +	struct ipe_policy __rcu **addr = NULL;
> +
> +	ino = d_inode(p->policyfs);
> +	addr = (struct ipe_policy __rcu **)&ino->i_private;
> +
> +	inode_lock(ino);
> +	rcu_assign_pointer(*addr, NULL);
> +	inode_unlock(ino);
> +	synchronize_rcu();
> +}
> +
> +/**
> + * ipe_del_policyfs_node - Delete a securityfs entry for @p.
> + * @p: Supplies a pointer to the policy to delete a securityfs entry for.
> + */
> +void ipe_del_policyfs_node(struct ipe_policy *p)
> +{
> +	if (IS_ERR_OR_NULL(p->policyfs))
> +		return;
> +
> +	soft_del_policyfs(p);
> +	securityfs_recursive_remove(p->policyfs);
> +}
> +
> +/**
> + * ipe_new_policyfs_node - Create a securityfs entry for @p.
> + * @p: Supplies a pointer to the policy to create a securityfs entry for.
> + *
> + * Return:
> + * * 0	- OK
> + * * !0	- Error
> + */
> +int ipe_new_policyfs_node(struct ipe_policy *p)
> +{
> +	int rc = 0;
> +	size_t i = 0;
> +	struct dentry *d = NULL;
> +	struct ipe_policy **addr = NULL;
> +	const struct ipefs_file *f = NULL;
> +
> +	p->policyfs = securityfs_create_dir(p->parsed->name, policy_root);
> +	if (IS_ERR(p->policyfs)) {
> +		rc = PTR_ERR(p->policyfs);
> +		goto err;
> +	}
> +
> +	addr = (struct ipe_policy **)&(d_inode(p->policyfs)->i_private);
> +	*addr = p;
> +
> +	for (i = 0; i < ARRAY_SIZE(policy_subdir); ++i) {
> +		f = &policy_subdir[i];
> +
> +		d = securityfs_create_file(f->name, f->access, p->policyfs, p->policyfs,
> +					   f->fops);
> +		if (IS_ERR(d)) {
> +			rc = PTR_ERR(d);
> +			goto err;
> +		}
> +	}
> +
> +	return 0;
> +err:
> +	ipe_del_policyfs_node(p);
> +	return rc;
> +}