Resguardo inicial

linux-7.2.3/security/safesetid/Kconfig

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: GPL-2.0-only
+config SECURITY_SAFESETID
+        bool "Gate setid transitions to limit CAP_SET{U/G}ID capabilities"
+        depends on SECURITY
+        select SECURITYFS
+        default n
+        help
+          SafeSetID is an LSM module that gates the setid family of syscalls to
+          restrict UID/GID transitions from a given UID/GID to only those
+          approved by a system-wide whitelist. These restrictions also prohibit
+          the given UIDs/GIDs from obtaining auxiliary privileges associated
+          with CAP_SET{U/G}ID, such as allowing a user to set up user namespace
+          UID mappings.
+
+          If you are unsure how to answer this question, answer N.

linux-7.2.3/security/safesetid/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+#
+# Makefile for the safesetid LSM.
+#
+
+obj-$(CONFIG_SECURITY_SAFESETID) := safesetid.o
+safesetid-y := lsm.o securityfs.o

linux-7.2.3/security/safesetid/lsm.c

@@ -0,0 +1,293 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SafeSetID Linux Security Module
+ *
+ * Author: Micah Morton <mortonm@chromium.org>
+ *
+ * Copyright (C) 2018 The Chromium OS Authors.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#define pr_fmt(fmt) "SafeSetID: " fmt
+
+#include <linux/lsm_hooks.h>
+#include <linux/module.h>
+#include <linux/ptrace.h>
+#include <linux/sched/task_stack.h>
+#include <linux/security.h>
+#include <uapi/linux/lsm.h>
+#include "lsm.h"
+
+/* Flag indicating whether initialization completed */
+int safesetid_initialized __initdata;
+
+struct setid_ruleset __rcu *safesetid_setuid_rules;
+struct setid_ruleset __rcu *safesetid_setgid_rules;
+
+
+/* Compute a decision for a transition from @src to @dst under @policy. */
+enum sid_policy_type _setid_policy_lookup(struct setid_ruleset *policy,
+		kid_t src, kid_t dst)
+{
+	struct setid_rule *rule;
+	enum sid_policy_type result = SIDPOL_DEFAULT;
+
+	if (policy->type == UID) {
+		hash_for_each_possible(policy->rules, rule, next, __kuid_val(src.uid)) {
+			if (!uid_eq(rule->src_id.uid, src.uid))
+				continue;
+			if (uid_eq(rule->dst_id.uid, dst.uid))
+				return SIDPOL_ALLOWED;
+			result = SIDPOL_CONSTRAINED;
+		}
+	} else if (policy->type == GID) {
+		hash_for_each_possible(policy->rules, rule, next, __kgid_val(src.gid)) {
+			if (!gid_eq(rule->src_id.gid, src.gid))
+				continue;
+			if (gid_eq(rule->dst_id.gid, dst.gid)){
+				return SIDPOL_ALLOWED;
+			}
+			result = SIDPOL_CONSTRAINED;
+		}
+	} else {
+		/* Should not reach here, report the ID as contrainsted */
+		result = SIDPOL_CONSTRAINED;
+	}
+	return result;
+}
+
+/*
+ * Compute a decision for a transition from @src to @dst under the active
+ * policy.
+ */
+static enum sid_policy_type setid_policy_lookup(kid_t src, kid_t dst, enum setid_type new_type)
+{
+	enum sid_policy_type result = SIDPOL_DEFAULT;
+	struct setid_ruleset *pol;
+
+	rcu_read_lock();
+	if (new_type == UID)
+		pol = rcu_dereference(safesetid_setuid_rules);
+	else if (new_type == GID)
+		pol = rcu_dereference(safesetid_setgid_rules);
+	else { /* Should not reach here */
+		result = SIDPOL_CONSTRAINED;
+		rcu_read_unlock();
+		return result;
+	}
+
+	if (pol) {
+		pol->type = new_type;
+		result = _setid_policy_lookup(pol, src, dst);
+	}
+	rcu_read_unlock();
+	return result;
+}
+
+static int safesetid_security_capable(const struct cred *cred,
+				      struct user_namespace *ns,
+				      int cap,
+				      unsigned int opts)
+{
+	/* We're only interested in CAP_SETUID and CAP_SETGID. */
+	if (cap != CAP_SETUID && cap != CAP_SETGID)
+		return 0;
+
+	/*
+	 * If CAP_SET{U/G}ID is currently used for a setid or setgroups syscall, we
+	 * want to let it go through here; the real security check happens later, in
+	 * the task_fix_set{u/g}id or task_fix_setgroups hooks.
+	 */
+	if ((opts & CAP_OPT_INSETID) != 0)
+		return 0;
+
+	switch (cap) {
+	case CAP_SETUID:
+		/*
+		* If no policy applies to this task, allow the use of CAP_SETUID for
+		* other purposes.
+		*/
+		if (setid_policy_lookup((kid_t){.uid = cred->uid}, INVALID_ID, UID) == SIDPOL_DEFAULT)
+			return 0;
+		/*
+		 * Reject use of CAP_SETUID for functionality other than calling
+		 * set*uid() (e.g. setting up userns uid mappings).
+		 */
+		pr_warn("Operation requires CAP_SETUID, which is not available to UID %u for operations besides approved set*uid transitions\n",
+			__kuid_val(cred->uid));
+		return -EPERM;
+	case CAP_SETGID:
+		/*
+		* If no policy applies to this task, allow the use of CAP_SETGID for
+		* other purposes.
+		*/
+		if (setid_policy_lookup((kid_t){.gid = cred->gid}, INVALID_ID, GID) == SIDPOL_DEFAULT)
+			return 0;
+		/*
+		 * Reject use of CAP_SETUID for functionality other than calling
+		 * set*gid() (e.g. setting up userns gid mappings).
+		 */
+		pr_warn("Operation requires CAP_SETGID, which is not available to GID %u for operations besides approved set*gid transitions\n",
+			__kgid_val(cred->gid));
+		return -EPERM;
+	default:
+		/* Error, the only capabilities were checking for is CAP_SETUID/GID */
+		return 0;
+	}
+	return 0;
+}
+
+/*
+ * Check whether a caller with old credentials @old is allowed to switch to
+ * credentials that contain @new_id.
+ */
+static bool id_permitted_for_cred(const struct cred *old, kid_t new_id, enum setid_type new_type)
+{
+	bool permitted;
+
+	/* If our old creds already had this ID in it, it's fine. */
+	if (new_type == UID) {
+		if (uid_eq(new_id.uid, old->uid) || uid_eq(new_id.uid, old->euid) ||
+			uid_eq(new_id.uid, old->suid))
+			return true;
+	} else if (new_type == GID){
+		if (gid_eq(new_id.gid, old->gid) || gid_eq(new_id.gid, old->egid) ||
+			gid_eq(new_id.gid, old->sgid))
+			return true;
+	} else /* Error, new_type is an invalid type */
+		return false;
+
+	/*
+	 * Transitions to new UIDs require a check against the policy of the old
+	 * RUID.
+	 */
+	permitted =
+	    setid_policy_lookup((kid_t){.uid = old->uid}, new_id, new_type) != SIDPOL_CONSTRAINED;
+
+	if (!permitted) {
+		if (new_type == UID) {
+			pr_warn("UID transition ((%d,%d,%d) -> %d) blocked\n",
+				__kuid_val(old->uid), __kuid_val(old->euid),
+				__kuid_val(old->suid), __kuid_val(new_id.uid));
+		} else if (new_type == GID) {
+			pr_warn("GID transition ((%d,%d,%d) -> %d) blocked\n",
+				__kgid_val(old->gid), __kgid_val(old->egid),
+				__kgid_val(old->sgid), __kgid_val(new_id.gid));
+		} else /* Error, new_type is an invalid type */
+			return false;
+	}
+	return permitted;
+}
+
+/*
+ * Check whether there is either an exception for user under old cred struct to
+ * set*uid to user under new cred struct, or the UID transition is allowed (by
+ * Linux set*uid rules) even without CAP_SETUID.
+ */
+static int safesetid_task_fix_setuid(struct cred *new,
+				     const struct cred *old,
+				     int flags)
+{
+
+	/* Do nothing if there are no setuid restrictions for our old RUID. */
+	if (setid_policy_lookup((kid_t){.uid = old->uid}, INVALID_ID, UID) == SIDPOL_DEFAULT)
+		return 0;
+
+	if (id_permitted_for_cred(old, (kid_t){.uid = new->uid}, UID) &&
+	    id_permitted_for_cred(old, (kid_t){.uid = new->euid}, UID) &&
+	    id_permitted_for_cred(old, (kid_t){.uid = new->suid}, UID) &&
+	    id_permitted_for_cred(old, (kid_t){.uid = new->fsuid}, UID))
+		return 0;
+
+	/*
+	 * Kill this process to avoid potential security vulnerabilities
+	 * that could arise from a missing allowlist entry preventing a
+	 * privileged process from dropping to a lesser-privileged one.
+	 */
+	force_sig(SIGKILL);
+	return -EACCES;
+}
+
+static int safesetid_task_fix_setgid(struct cred *new,
+				     const struct cred *old,
+				     int flags)
+{
+
+	/* Do nothing if there are no setgid restrictions for our old RGID. */
+	if (setid_policy_lookup((kid_t){.gid = old->gid}, INVALID_ID, GID) == SIDPOL_DEFAULT)
+		return 0;
+
+	if (id_permitted_for_cred(old, (kid_t){.gid = new->gid}, GID) &&
+	    id_permitted_for_cred(old, (kid_t){.gid = new->egid}, GID) &&
+	    id_permitted_for_cred(old, (kid_t){.gid = new->sgid}, GID) &&
+	    id_permitted_for_cred(old, (kid_t){.gid = new->fsgid}, GID))
+		return 0;
+
+	/*
+	 * Kill this process to avoid potential security vulnerabilities
+	 * that could arise from a missing allowlist entry preventing a
+	 * privileged process from dropping to a lesser-privileged one.
+	 */
+	force_sig(SIGKILL);
+	return -EACCES;
+}
+
+static int safesetid_task_fix_setgroups(struct cred *new, const struct cred *old)
+{
+	int i;
+
+	/* Do nothing if there are no setgid restrictions for our old RGID. */
+	if (setid_policy_lookup((kid_t){.gid = old->gid}, INVALID_ID, GID) == SIDPOL_DEFAULT)
+		return 0;
+
+	get_group_info(new->group_info);
+	for (i = 0; i < new->group_info->ngroups; i++) {
+		if (!id_permitted_for_cred(old, (kid_t){.gid = new->group_info->gid[i]}, GID)) {
+			put_group_info(new->group_info);
+			/*
+			 * Kill this process to avoid potential security vulnerabilities
+			 * that could arise from a missing allowlist entry preventing a
+			 * privileged process from dropping to a lesser-privileged one.
+			 */
+			force_sig(SIGKILL);
+			return -EACCES;
+		}
+	}
+
+	put_group_info(new->group_info);
+	return 0;
+}
+
+static const struct lsm_id safesetid_lsmid = {
+	.name = "safesetid",
+	.id = LSM_ID_SAFESETID,
+};
+
+static struct security_hook_list safesetid_security_hooks[] = {
+	LSM_HOOK_INIT(task_fix_setuid, safesetid_task_fix_setuid),
+	LSM_HOOK_INIT(task_fix_setgid, safesetid_task_fix_setgid),
+	LSM_HOOK_INIT(task_fix_setgroups, safesetid_task_fix_setgroups),
+	LSM_HOOK_INIT(capable, safesetid_security_capable)
+};
+
+static int __init safesetid_security_init(void)
+{
+	security_add_hooks(safesetid_security_hooks,
+			   ARRAY_SIZE(safesetid_security_hooks),
+			   &safesetid_lsmid);
+
+	/* Report that SafeSetID successfully initialized */
+	safesetid_initialized = 1;
+
+	return 0;
+}
+
+DEFINE_LSM(safesetid_security_init) = {
+	.id = &safesetid_lsmid,
+	.init = safesetid_security_init,
+	.initcall_fs = safesetid_init_securityfs,
+};

linux-7.2.3/security/safesetid/lsm.h

@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * SafeSetID Linux Security Module
+ *
+ * Author: Micah Morton <mortonm@chromium.org>
+ *
+ * Copyright (C) 2018 The Chromium OS Authors.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+#ifndef _SAFESETID_H
+#define _SAFESETID_H
+
+#include <linux/types.h>
+#include <linux/uidgid.h>
+#include <linux/hashtable.h>
+
+/* Flag indicating whether initialization completed */
+extern int safesetid_initialized __initdata;
+
+enum sid_policy_type {
+	SIDPOL_DEFAULT, /* source ID is unaffected by policy */
+	SIDPOL_CONSTRAINED, /* source ID is affected by policy */
+	SIDPOL_ALLOWED /* target ID explicitly allowed */
+};
+
+typedef union {
+	kuid_t uid;
+	kgid_t gid;
+} kid_t;
+
+enum setid_type {
+	UID,
+	GID
+};
+
+/*
+ * Hash table entry to store safesetid policy signifying that 'src_id'
+ * can set*id to 'dst_id'.
+ */
+struct setid_rule {
+	struct hlist_node next;
+	kid_t src_id;
+	kid_t dst_id;
+
+	/* Flag to signal if rule is for UID's or GID's */
+	enum setid_type type;
+};
+
+#define SETID_HASH_BITS 8 /* 256 buckets in hash table */
+
+/* Extension of INVALID_UID/INVALID_GID for kid_t type */
+#define INVALID_ID (kid_t){.uid = INVALID_UID}
+
+struct setid_ruleset {
+	DECLARE_HASHTABLE(rules, SETID_HASH_BITS);
+	char *policy_str;
+	struct rcu_head rcu;
+
+	//Flag to signal if ruleset is for UID's or GID's
+	enum setid_type type;
+};
+
+enum sid_policy_type _setid_policy_lookup(struct setid_ruleset *policy,
+		kid_t src, kid_t dst);
+
+extern struct setid_ruleset __rcu *safesetid_setuid_rules;
+extern struct setid_ruleset __rcu *safesetid_setgid_rules;
+
+int safesetid_init_securityfs(void);
+
+#endif /* _SAFESETID_H */

linux-7.2.3/security/safesetid/securityfs.c

@@ -0,0 +1,347 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * SafeSetID Linux Security Module
+ *
+ * Author: Micah Morton <mortonm@chromium.org>
+ *
+ * Copyright (C) 2018 The Chromium OS Authors.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2, as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#define pr_fmt(fmt) "SafeSetID: " fmt
+
+#include <linux/security.h>
+#include <linux/cred.h>
+
+#include "lsm.h"
+
+static DEFINE_MUTEX(uid_policy_update_lock);
+static DEFINE_MUTEX(gid_policy_update_lock);
+
+/*
+ * In the case the input buffer contains one or more invalid IDs, the kid_t
+ * variables pointed to by @parent and @child will get updated but this
+ * function will return an error.
+ * Contents of @buf may be modified.
+ */
+static int parse_policy_line(struct file *file, char *buf,
+	struct setid_rule *rule)
+{
+	char *child_str;
+	int ret;
+	u32 parsed_parent, parsed_child;
+
+	/* Format of |buf| string should be <UID>:<UID> or <GID>:<GID> */
+	child_str = strchr(buf, ':');
+	if (child_str == NULL)
+		return -EINVAL;
+	*child_str = '\0';
+	child_str++;
+
+	ret = kstrtou32(buf, 0, &parsed_parent);
+	if (ret)
+		return ret;
+
+	ret = kstrtou32(child_str, 0, &parsed_child);
+	if (ret)
+		return ret;
+
+	if (rule->type == UID){
+		rule->src_id.uid = make_kuid(file->f_cred->user_ns, parsed_parent);
+		rule->dst_id.uid = make_kuid(file->f_cred->user_ns, parsed_child);
+		if (!uid_valid(rule->src_id.uid) || !uid_valid(rule->dst_id.uid))
+			return -EINVAL;
+	} else if (rule->type == GID){
+		rule->src_id.gid = make_kgid(file->f_cred->user_ns, parsed_parent);
+		rule->dst_id.gid = make_kgid(file->f_cred->user_ns, parsed_child);
+		if (!gid_valid(rule->src_id.gid) || !gid_valid(rule->dst_id.gid))
+			return -EINVAL;
+	} else {
+		/* Error, rule->type is an invalid type */
+		return -EINVAL;
+	}
+	return 0;
+}
+
+static void __release_ruleset(struct rcu_head *rcu)
+{
+	struct setid_ruleset *pol =
+		container_of(rcu, struct setid_ruleset, rcu);
+	int bucket;
+	struct setid_rule *rule;
+	struct hlist_node *tmp;
+
+	hash_for_each_safe(pol->rules, bucket, tmp, rule, next)
+		kfree(rule);
+	kfree(pol->policy_str);
+	kfree(pol);
+}
+
+static void release_ruleset(struct setid_ruleset *pol){
+	call_rcu(&pol->rcu, __release_ruleset);
+}
+
+static void insert_rule(struct setid_ruleset *pol, struct setid_rule *rule)
+{
+	if (pol->type == UID)
+		hash_add(pol->rules, &rule->next, __kuid_val(rule->src_id.uid));
+	else if (pol->type == GID)
+		hash_add(pol->rules, &rule->next, __kgid_val(rule->src_id.gid));
+	else /* Error, pol->type is neither UID or GID */
+		return;
+}
+
+static int verify_ruleset(struct setid_ruleset *pol)
+{
+	int bucket;
+	struct setid_rule *rule, *nrule;
+	int res = 0;
+
+	hash_for_each(pol->rules, bucket, rule, next) {
+		if (_setid_policy_lookup(pol, rule->dst_id, INVALID_ID) == SIDPOL_DEFAULT) {
+			if (pol->type == UID) {
+				pr_warn("insecure policy detected: uid %d is constrained but transitively unconstrained through uid %d\n",
+					__kuid_val(rule->src_id.uid),
+					__kuid_val(rule->dst_id.uid));
+			} else if (pol->type == GID) {
+				pr_warn("insecure policy detected: gid %d is constrained but transitively unconstrained through gid %d\n",
+					__kgid_val(rule->src_id.gid),
+					__kgid_val(rule->dst_id.gid));
+			} else { /* pol->type is an invalid type */
+				res = -EINVAL;
+				return res;
+			}
+			res = -EINVAL;
+
+			/* fix it up */
+			nrule = kmalloc_obj(struct setid_rule);
+			if (!nrule)
+				return -ENOMEM;
+			if (pol->type == UID){
+				nrule->src_id.uid = rule->dst_id.uid;
+				nrule->dst_id.uid = rule->dst_id.uid;
+				nrule->type = UID;
+			} else { /* pol->type must be GID if we've made it to here */
+				nrule->src_id.gid = rule->dst_id.gid;
+				nrule->dst_id.gid = rule->dst_id.gid;
+				nrule->type = GID;
+			}
+			insert_rule(pol, nrule);
+		}
+	}
+	return res;
+}
+
+static ssize_t handle_policy_update(struct file *file,
+				    const char __user *ubuf, size_t len, enum setid_type policy_type)
+{
+	struct setid_ruleset *pol;
+	char *buf, *p, *end;
+	int err;
+
+	if (len >= KMALLOC_MAX_SIZE)
+		return -EINVAL;
+
+	pol = kmalloc_obj(struct setid_ruleset);
+	if (!pol)
+		return -ENOMEM;
+	pol->policy_str = NULL;
+	pol->type = policy_type;
+	hash_init(pol->rules);
+
+	p = buf = memdup_user_nul(ubuf, len);
+	if (IS_ERR(buf)) {
+		err = PTR_ERR(buf);
+		goto out_free_pol;
+	}
+	pol->policy_str = kstrdup(buf, GFP_KERNEL);
+	if (pol->policy_str == NULL) {
+		err = -ENOMEM;
+		goto out_free_buf;
+	}
+
+	/* policy lines, including the last one, end with \n */
+	while (*p != '\0') {
+		struct setid_rule *rule;
+
+		end = strchr(p, '\n');
+		if (end == NULL) {
+			err = -EINVAL;
+			goto out_free_buf;
+		}
+		*end = '\0';
+
+		rule = kmalloc_obj(struct setid_rule);
+		if (!rule) {
+			err = -ENOMEM;
+			goto out_free_buf;
+		}
+
+		rule->type = policy_type;
+		err = parse_policy_line(file, p, rule);
+		if (err)
+			goto out_free_rule;
+
+		if (_setid_policy_lookup(pol, rule->src_id, rule->dst_id) == SIDPOL_ALLOWED) {
+			pr_warn("bad policy: duplicate entry\n");
+			err = -EEXIST;
+			goto out_free_rule;
+		}
+
+		insert_rule(pol, rule);
+		p = end + 1;
+		continue;
+
+out_free_rule:
+		kfree(rule);
+		goto out_free_buf;
+	}
+
+	err = verify_ruleset(pol);
+	/* bogus policy falls through after fixing it up */
+	if (err && err != -EINVAL)
+		goto out_free_buf;
+
+	/*
+	 * Everything looks good, apply the policy and release the old one.
+	 * What we really want here is an xchg() wrapper for RCU, but since that
+	 * doesn't currently exist, just use a spinlock for now.
+	 */
+	if (policy_type == UID) {
+		mutex_lock(&uid_policy_update_lock);
+		pol = rcu_replace_pointer(safesetid_setuid_rules, pol,
+					  lockdep_is_held(&uid_policy_update_lock));
+		mutex_unlock(&uid_policy_update_lock);
+	} else if (policy_type == GID) {
+		mutex_lock(&gid_policy_update_lock);
+		pol = rcu_replace_pointer(safesetid_setgid_rules, pol,
+					  lockdep_is_held(&gid_policy_update_lock));
+		mutex_unlock(&gid_policy_update_lock);
+	} else {
+		/* Error, policy type is neither UID or GID */
+		pr_warn("error: bad policy type");
+	}
+	err = len;
+
+out_free_buf:
+	kfree(buf);
+out_free_pol:
+	if (pol)
+		release_ruleset(pol);
+	return err;
+}
+
+static ssize_t safesetid_uid_file_write(struct file *file,
+				    const char __user *buf,
+				    size_t len,
+				    loff_t *ppos)
+{
+	if (!file_ns_capable(file, &init_user_ns, CAP_MAC_ADMIN))
+		return -EPERM;
+
+	if (*ppos != 0)
+		return -EINVAL;
+
+	return handle_policy_update(file, buf, len, UID);
+}
+
+static ssize_t safesetid_gid_file_write(struct file *file,
+				    const char __user *buf,
+				    size_t len,
+				    loff_t *ppos)
+{
+	if (!file_ns_capable(file, &init_user_ns, CAP_MAC_ADMIN))
+		return -EPERM;
+
+	if (*ppos != 0)
+		return -EINVAL;
+
+	return handle_policy_update(file, buf, len, GID);
+}
+
+static ssize_t safesetid_file_read(struct file *file, char __user *buf,
+				   size_t len, loff_t *ppos, struct mutex *policy_update_lock, struct __rcu setid_ruleset* ruleset)
+{
+	ssize_t res = 0;
+	struct setid_ruleset *pol;
+	const char *kbuf;
+
+	mutex_lock(policy_update_lock);
+	pol = rcu_dereference_protected(ruleset, lockdep_is_held(policy_update_lock));
+	if (pol) {
+		kbuf = pol->policy_str;
+		res = simple_read_from_buffer(buf, len, ppos,
+					      kbuf, strlen(kbuf));
+	}
+	mutex_unlock(policy_update_lock);
+
+	return res;
+}
+
+static ssize_t safesetid_uid_file_read(struct file *file, char __user *buf,
+				   size_t len, loff_t *ppos)
+{
+	return safesetid_file_read(file, buf, len, ppos,
+				   &uid_policy_update_lock, safesetid_setuid_rules);
+}
+
+static ssize_t safesetid_gid_file_read(struct file *file, char __user *buf,
+				   size_t len, loff_t *ppos)
+{
+	return safesetid_file_read(file, buf, len, ppos,
+				   &gid_policy_update_lock, safesetid_setgid_rules);
+}
+
+
+
+static const struct file_operations safesetid_uid_file_fops = {
+	.read = safesetid_uid_file_read,
+	.write = safesetid_uid_file_write,
+};
+
+static const struct file_operations safesetid_gid_file_fops = {
+	.read = safesetid_gid_file_read,
+	.write = safesetid_gid_file_write,
+};
+
+int __init safesetid_init_securityfs(void)
+{
+	int ret;
+	struct dentry *policy_dir;
+	struct dentry *uid_policy_file;
+	struct dentry *gid_policy_file;
+
+	if (!safesetid_initialized)
+		return 0;
+
+	policy_dir = securityfs_create_dir("safesetid", NULL);
+	if (IS_ERR(policy_dir)) {
+		ret = PTR_ERR(policy_dir);
+		goto error;
+	}
+
+	uid_policy_file = securityfs_create_file("uid_allowlist_policy", 0600,
+			policy_dir, NULL, &safesetid_uid_file_fops);
+	if (IS_ERR(uid_policy_file)) {
+		ret = PTR_ERR(uid_policy_file);
+		goto error;
+	}
+
+	gid_policy_file = securityfs_create_file("gid_allowlist_policy", 0600,
+			policy_dir, NULL, &safesetid_gid_file_fops);
+	if (IS_ERR(gid_policy_file)) {
+		ret = PTR_ERR(gid_policy_file);
+		goto error;
+	}
+
+
+	return 0;
+
+error:
+	securityfs_remove(policy_dir);
+	return ret;
+}