// SPDX-License-Identifier: GPL-2.0-or-later

  /* Task credentials management - see Documentation/security/credentials.rst

   *
   * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)

   */

  #include <linux/export.h>

  #include <linux/cred.h>

  #include <linux/slab.h>

  #include <linux/sched.h>

  #include <linux/sched/coredump.h>

  #include <linux/key.h>
  #include <linux/keyctl.h>
  #include <linux/init_task.h>
  #include <linux/security.h>

  #include <linux/binfmts.h>

  #include <linux/cn_proc.h>

  #include <linux/uidgid.h>

  #if 0

  #define kdebug(FMT, ...)						\
  	printk("[%-5.5s%5u] " FMT "
  ",					\
  	       current->comm, current->pid, ##__VA_ARGS__)

  #else

  #define kdebug(FMT, ...)						\
  do {									\
  	if (0)								\
  		no_printk("[%-5.5s%5u] " FMT "
  ",			\
  			  current->comm, current->pid, ##__VA_ARGS__);	\
  } while (0)

  #endif

  static struct kmem_cache *cred_jar;

  /* init to 2 - one for init_task, one to ensure it is never freed */
  struct group_info init_groups = { .usage = ATOMIC_INIT(2) };

  /*
   * The initial credentials for the initial task
   */
  struct cred init_cred = {

  	.usage			= ATOMIC_INIT(4),

  #ifdef CONFIG_DEBUG_CREDENTIALS
  	.subscribers		= ATOMIC_INIT(2),
  	.magic			= CRED_MAGIC,
  #endif

  	.uid			= GLOBAL_ROOT_UID,
  	.gid			= GLOBAL_ROOT_GID,
  	.suid			= GLOBAL_ROOT_UID,
  	.sgid			= GLOBAL_ROOT_GID,
  	.euid			= GLOBAL_ROOT_UID,
  	.egid			= GLOBAL_ROOT_GID,
  	.fsuid			= GLOBAL_ROOT_UID,
  	.fsgid			= GLOBAL_ROOT_GID,

  	.securebits		= SECUREBITS_DEFAULT,

  	.cap_inheritable	= CAP_EMPTY_SET,

  	.cap_permitted		= CAP_FULL_SET,

  	.cap_effective		= CAP_FULL_SET,
  	.cap_bset		= CAP_FULL_SET,

  	.user			= INIT_USER,

  	.user_ns		= &init_user_ns,

  	.group_info		= &init_groups,
  };

  static inline void set_cred_subscribers(struct cred *cred, int n)
  {
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	atomic_set(&cred->subscribers, n);
  #endif
  }
  
  static inline int read_cred_subscribers(const struct cred *cred)
  {
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	return atomic_read(&cred->subscribers);
  #else
  	return 0;
  #endif
  }
  
  static inline void alter_cred_subscribers(const struct cred *_cred, int n)
  {
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	struct cred *cred = (struct cred *) _cred;
  
  	atomic_add(n, &cred->subscribers);
  #endif
  }

  /*
   * The RCU callback to actually dispose of a set of credentials
   */
  static void put_cred_rcu(struct rcu_head *rcu)
  {
  	struct cred *cred = container_of(rcu, struct cred, rcu);

  	kdebug("put_cred_rcu(%p)", cred);
  
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	if (cred->magic != CRED_MAGIC_DEAD ||
  	    atomic_read(&cred->usage) != 0 ||
  	    read_cred_subscribers(cred) != 0)
  		panic("CRED: put_cred_rcu() sees %p with"
  		      " mag %x, put %p, usage %d, subscr %d
  ",
  		      cred, cred->magic, cred->put_addr,
  		      atomic_read(&cred->usage),
  		      read_cred_subscribers(cred));
  #else

  	if (atomic_read(&cred->usage) != 0)
  		panic("CRED: put_cred_rcu() sees %p with usage %d
  ",
  		      cred, atomic_read(&cred->usage));

  #endif

  	security_cred_free(cred);

  	key_put(cred->session_keyring);
  	key_put(cred->process_keyring);

  	key_put(cred->thread_keyring);
  	key_put(cred->request_key_auth);

  	if (cred->group_info)
  		put_group_info(cred->group_info);

  	free_uid(cred->user);

  	put_user_ns(cred->user_ns);

  	kmem_cache_free(cred_jar, cred);

  }
  
  /**
   * __put_cred - Destroy a set of credentials

   * @cred: The record to release

   *
   * Destroy a set of credentials on which no references remain.
   */
  void __put_cred(struct cred *cred)
  {

  	kdebug("__put_cred(%p{%d,%d})", cred,
  	       atomic_read(&cred->usage),
  	       read_cred_subscribers(cred));

  	BUG_ON(atomic_read(&cred->usage) != 0);

  #ifdef CONFIG_DEBUG_CREDENTIALS
  	BUG_ON(read_cred_subscribers(cred) != 0);
  	cred->magic = CRED_MAGIC_DEAD;
  	cred->put_addr = __builtin_return_address(0);
  #endif
  	BUG_ON(cred == current->cred);
  	BUG_ON(cred == current->real_cred);

  	if (cred->non_rcu)
  		put_cred_rcu(&cred->rcu);
  	else
  		call_rcu(&cred->rcu, put_cred_rcu);

  }
  EXPORT_SYMBOL(__put_cred);

  /*
   * Clean up a task's credentials when it exits
   */
  void exit_creds(struct task_struct *tsk)
  {
  	struct cred *cred;
  
  	kdebug("exit_creds(%u,%p,%p,{%d,%d})", tsk->pid, tsk->real_cred, tsk->cred,
  	       atomic_read(&tsk->cred->usage),
  	       read_cred_subscribers(tsk->cred));
  
  	cred = (struct cred *) tsk->real_cred;
  	tsk->real_cred = NULL;
  	validate_creds(cred);
  	alter_cred_subscribers(cred, -1);
  	put_cred(cred);
  
  	cred = (struct cred *) tsk->cred;
  	tsk->cred = NULL;
  	validate_creds(cred);
  	alter_cred_subscribers(cred, -1);
  	put_cred(cred);

  
  #ifdef CONFIG_KEYS_REQUEST_CACHE

  	key_put(tsk->cached_requested_key);
  	tsk->cached_requested_key = NULL;

  #endif

  }

  /**
   * get_task_cred - Get another task's objective credentials
   * @task: The task to query
   *
   * Get the objective credentials of a task, pinning them so that they can't go
   * away.  Accessing a task's credentials directly is not permitted.
   *
   * The caller must also make sure task doesn't get deleted, either by holding a
   * ref on task or by holding tasklist_lock to prevent it from being unlinked.
   */
  const struct cred *get_task_cred(struct task_struct *task)
  {
  	const struct cred *cred;
  
  	rcu_read_lock();
  
  	do {
  		cred = __task_cred((task));
  		BUG_ON(!cred);

  	} while (!get_cred_rcu(cred));

  
  	rcu_read_unlock();
  	return cred;
  }

  EXPORT_SYMBOL(get_task_cred);

  /*
   * Allocate blank credentials, such that the credentials can be filled in at a
   * later date without risk of ENOMEM.
   */
  struct cred *cred_alloc_blank(void)
  {
  	struct cred *new;
  
  	new = kmem_cache_zalloc(cred_jar, GFP_KERNEL);
  	if (!new)
  		return NULL;

  	atomic_set(&new->usage, 1);

  #ifdef CONFIG_DEBUG_CREDENTIALS
  	new->magic = CRED_MAGIC;
  #endif

  	if (security_cred_alloc_blank(new, GFP_KERNEL_ACCOUNT) < 0)

  		goto error;

  	return new;
  
  error:
  	abort_creds(new);
  	return NULL;

  }

  /**
   * prepare_creds - Prepare a new set of credentials for modification
   *
   * Prepare a new set of task credentials for modification.  A task's creds
   * shouldn't generally be modified directly, therefore this function is used to
   * prepare a new copy, which the caller then modifies and then commits by
   * calling commit_creds().
   *

   * Preparation involves making a copy of the objective creds for modification.
   *

   * Returns a pointer to the new creds-to-be if successful, NULL otherwise.
   *
   * Call commit_creds() or abort_creds() to clean up.
   */
  struct cred *prepare_creds(void)
  {
  	struct task_struct *task = current;
  	const struct cred *old;
  	struct cred *new;

  	validate_process_creds();

  
  	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
  	if (!new)
  		return NULL;

  	kdebug("prepare_creds() alloc %p", new);

  	old = task->cred;
  	memcpy(new, old, sizeof(struct cred));

  	new->non_rcu = 0;

  	atomic_set(&new->usage, 1);

  	set_cred_subscribers(new, 0);

  	get_group_info(new->group_info);
  	get_uid(new->user);

  	get_user_ns(new->user_ns);

  
  #ifdef CONFIG_KEYS

  	key_get(new->session_keyring);
  	key_get(new->process_keyring);

  	key_get(new->thread_keyring);
  	key_get(new->request_key_auth);

  #endif
  
  #ifdef CONFIG_SECURITY
  	new->security = NULL;
  #endif

  	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)

  		goto error;

  	validate_creds(new);

  	return new;
  
  error:
  	abort_creds(new);
  	return NULL;
  }
  EXPORT_SYMBOL(prepare_creds);
  
  /*

   * Prepare credentials for current to perform an execve()

   * - The caller must hold ->cred_guard_mutex

   */
  struct cred *prepare_exec_creds(void)
  {

  	struct cred *new;

  	new = prepare_creds();

  	if (!new)

  		return new;

  
  #ifdef CONFIG_KEYS
  	/* newly exec'd tasks don't get a thread keyring */
  	key_put(new->thread_keyring);
  	new->thread_keyring = NULL;

  	/* inherit the session keyring; new process keyring */

  	key_put(new->process_keyring);
  	new->process_keyring = NULL;

  #endif

  	new->suid = new->fsuid = new->euid;
  	new->sgid = new->fsgid = new->egid;

  	return new;
  }
  
  /*

   * Copy credentials for the new process created by fork()

   *
   * We share if we can, but under some circumstances we have to generate a new
   * set.

   *
   * The new process gets the current process's subjective credentials as its
   * objective and subjective credentials

   */
  int copy_creds(struct task_struct *p, unsigned long clone_flags)
  {

  	struct cred *new;

  	int ret;

  #ifdef CONFIG_KEYS_REQUEST_CACHE
  	p->cached_requested_key = NULL;
  #endif

  	if (
  #ifdef CONFIG_KEYS
  		!p->cred->thread_keyring &&
  #endif
  		clone_flags & CLONE_THREAD
  	    ) {

  		p->real_cred = get_cred(p->cred);

  		get_cred(p->cred);

  		alter_cred_subscribers(p->cred, 2);
  		kdebug("share_creds(%p{%d,%d})",
  		       p->cred, atomic_read(&p->cred->usage),
  		       read_cred_subscribers(p->cred));

  		atomic_inc(&p->cred->user->processes);
  		return 0;
  	}
  
  	new = prepare_creds();
  	if (!new)

  		return -ENOMEM;

  	if (clone_flags & CLONE_NEWUSER) {
  		ret = create_user_ns(new);
  		if (ret < 0)
  			goto error_put;
  	}

  #ifdef CONFIG_KEYS

  	/* new threads get their own thread keyrings if their parent already
  	 * had one */
  	if (new->thread_keyring) {
  		key_put(new->thread_keyring);
  		new->thread_keyring = NULL;
  		if (clone_flags & CLONE_THREAD)
  			install_thread_keyring_to_cred(new);
  	}

  	/* The process keyring is only shared between the threads in a process;
  	 * anything outside of those threads doesn't inherit.
  	 */

  	if (!(clone_flags & CLONE_THREAD)) {

  		key_put(new->process_keyring);
  		new->process_keyring = NULL;

  	}
  #endif

  	atomic_inc(&new->user->processes);

  	p->cred = p->real_cred = get_cred(new);

  	alter_cred_subscribers(new, 2);
  	validate_creds(new);

  	return 0;

  
  error_put:
  	put_cred(new);
  	return ret;

  }

  static bool cred_cap_issubset(const struct cred *set, const struct cred *subset)
  {
  	const struct user_namespace *set_ns = set->user_ns;
  	const struct user_namespace *subset_ns = subset->user_ns;
  
  	/* If the two credentials are in the same user namespace see if
  	 * the capabilities of subset are a subset of set.
  	 */
  	if (set_ns == subset_ns)
  		return cap_issubset(subset->cap_permitted, set->cap_permitted);
  
  	/* The credentials are in a different user namespaces
  	 * therefore one is a subset of the other only if a set is an
  	 * ancestor of subset and set->euid is owner of subset or one
  	 * of subsets ancestors.
  	 */
  	for (;subset_ns != &init_user_ns; subset_ns = subset_ns->parent) {
  		if ((set_ns == subset_ns->parent)  &&
  		    uid_eq(subset_ns->owner, set->euid))
  			return true;
  	}
  
  	return false;
  }

  /**
   * commit_creds - Install new credentials upon the current task
   * @new: The credentials to be assigned
   *
   * Install a new set of credentials to the current task, using RCU to replace

   * the old set.  Both the objective and the subjective credentials pointers are
   * updated.  This function may not be called if the subjective credentials are
   * in an overridden state.

   *
   * This function eats the caller's reference to the new credentials.
   *
   * Always returns 0 thus allowing this function to be tail-called at the end
   * of, say, sys_setgid().
   */
  int commit_creds(struct cred *new)
  {
  	struct task_struct *task = current;

  	const struct cred *old = task->real_cred;

  	kdebug("commit_creds(%p{%d,%d})", new,
  	       atomic_read(&new->usage),
  	       read_cred_subscribers(new));
  
  	BUG_ON(task->cred != old);
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	BUG_ON(read_cred_subscribers(old) < 2);
  	validate_creds(old);
  	validate_creds(new);
  #endif

  	BUG_ON(atomic_read(&new->usage) < 1);

  	get_cred(new); /* we will require a ref for the subj creds too */

  	/* dumpability changes */

  	if (!uid_eq(old->euid, new->euid) ||
  	    !gid_eq(old->egid, new->egid) ||
  	    !uid_eq(old->fsuid, new->fsuid) ||
  	    !gid_eq(old->fsgid, new->fsgid) ||

  	    !cred_cap_issubset(old, new)) {

  		if (task->mm)
  			set_dumpable(task->mm, suid_dumpable);

  		task->pdeath_signal = 0;

  		/*
  		 * If a task drops privileges and becomes nondumpable,
  		 * the dumpability change must become visible before
  		 * the credential change; otherwise, a __ptrace_may_access()
  		 * racing with this change may be able to attach to a task it
  		 * shouldn't be able to attach to (as if the task had dropped
  		 * privileges without becoming nondumpable).
  		 * Pairs with a read barrier in __ptrace_may_access().
  		 */

  		smp_wmb();

  	}

  	/* alter the thread keyring */

  	if (!uid_eq(new->fsuid, old->fsuid))

  		key_fsuid_changed(new);

  	if (!gid_eq(new->fsgid, old->fsgid))

  		key_fsgid_changed(new);

  
  	/* do it

  	 * RLIMIT_NPROC limits on user->processes have already been checked
  	 * in set_user().

  	 */

  	alter_cred_subscribers(new, 2);

  	if (new->user != old->user)
  		atomic_inc(&new->user->processes);

  	rcu_assign_pointer(task->real_cred, new);

  	rcu_assign_pointer(task->cred, new);
  	if (new->user != old->user)
  		atomic_dec(&old->user->processes);

  	alter_cred_subscribers(old, -2);

  	/* send notifications */

  	if (!uid_eq(new->uid,   old->uid)  ||
  	    !uid_eq(new->euid,  old->euid) ||
  	    !uid_eq(new->suid,  old->suid) ||
  	    !uid_eq(new->fsuid, old->fsuid))

  		proc_id_connector(task, PROC_EVENT_UID);

  	if (!gid_eq(new->gid,   old->gid)  ||
  	    !gid_eq(new->egid,  old->egid) ||
  	    !gid_eq(new->sgid,  old->sgid) ||
  	    !gid_eq(new->fsgid, old->fsgid))

  		proc_id_connector(task, PROC_EVENT_GID);

  	/* release the old obj and subj refs both */
  	put_cred(old);

  	put_cred(old);

  	return 0;
  }

  EXPORT_SYMBOL(commit_creds);
  
  /**
   * abort_creds - Discard a set of credentials and unlock the current task
   * @new: The credentials that were going to be applied
   *
   * Discard a set of credentials that were under construction and unlock the
   * current task.
   */
  void abort_creds(struct cred *new)
  {

  	kdebug("abort_creds(%p{%d,%d})", new,
  	       atomic_read(&new->usage),
  	       read_cred_subscribers(new));
  
  #ifdef CONFIG_DEBUG_CREDENTIALS
  	BUG_ON(read_cred_subscribers(new) != 0);
  #endif

  	BUG_ON(atomic_read(&new->usage) < 1);
  	put_cred(new);
  }
  EXPORT_SYMBOL(abort_creds);
  
  /**

   * override_creds - Override the current process's subjective credentials

   * @new: The credentials to be assigned
   *

   * Install a set of temporary override subjective credentials on the current
   * process, returning the old set for later reversion.

   */
  const struct cred *override_creds(const struct cred *new)
  {
  	const struct cred *old = current->cred;

  	kdebug("override_creds(%p{%d,%d})", new,
  	       atomic_read(&new->usage),
  	       read_cred_subscribers(new));
  
  	validate_creds(old);
  	validate_creds(new);

  
  	/*
  	 * NOTE! This uses 'get_new_cred()' rather than 'get_cred()'.
  	 *
  	 * That means that we do not clear the 'non_rcu' flag, since
  	 * we are only installing the cred into the thread-synchronous
  	 * '->cred' pointer, not the '->real_cred' pointer that is
  	 * visible to other threads under RCU.
  	 *
  	 * Also note that we did validate_creds() manually, not depending
  	 * on the validation in 'get_cred()'.
  	 */
  	get_new_cred((struct cred *)new);

  	alter_cred_subscribers(new, 1);
  	rcu_assign_pointer(current->cred, new);
  	alter_cred_subscribers(old, -1);
  
  	kdebug("override_creds() = %p{%d,%d}", old,
  	       atomic_read(&old->usage),
  	       read_cred_subscribers(old));

  	return old;
  }
  EXPORT_SYMBOL(override_creds);
  
  /**

   * revert_creds - Revert a temporary subjective credentials override

   * @old: The credentials to be restored
   *

   * Revert a temporary set of override subjective credentials to an old set,
   * discarding the override set.

   */
  void revert_creds(const struct cred *old)
  {
  	const struct cred *override = current->cred;

  	kdebug("revert_creds(%p{%d,%d})", old,
  	       atomic_read(&old->usage),
  	       read_cred_subscribers(old));
  
  	validate_creds(old);
  	validate_creds(override);
  	alter_cred_subscribers(old, 1);

  	rcu_assign_pointer(current->cred, old);

  	alter_cred_subscribers(override, -1);

  	put_cred(override);
  }
  EXPORT_SYMBOL(revert_creds);

  /**
   * cred_fscmp - Compare two credentials with respect to filesystem access.
   * @a: The first credential
   * @b: The second credential
   *
   * cred_cmp() will return zero if both credentials have the same
   * fsuid, fsgid, and supplementary groups.  That is, if they will both
   * provide the same access to files based on mode/uid/gid.
   * If the credentials are different, then either -1 or 1 will
   * be returned depending on whether @a comes before or after @b
   * respectively in an arbitrary, but stable, ordering of credentials.
   *
   * Return: -1, 0, or 1 depending on comparison
   */
  int cred_fscmp(const struct cred *a, const struct cred *b)
  {
  	struct group_info *ga, *gb;
  	int g;
  
  	if (a == b)
  		return 0;
  	if (uid_lt(a->fsuid, b->fsuid))
  		return -1;
  	if (uid_gt(a->fsuid, b->fsuid))
  		return 1;
  
  	if (gid_lt(a->fsgid, b->fsgid))
  		return -1;
  	if (gid_gt(a->fsgid, b->fsgid))
  		return 1;
  
  	ga = a->group_info;
  	gb = b->group_info;
  	if (ga == gb)
  		return 0;
  	if (ga == NULL)
  		return -1;
  	if (gb == NULL)
  		return 1;
  	if (ga->ngroups < gb->ngroups)
  		return -1;
  	if (ga->ngroups > gb->ngroups)
  		return 1;
  
  	for (g = 0; g < ga->ngroups; g++) {
  		if (gid_lt(ga->gid[g], gb->gid[g]))
  			return -1;
  		if (gid_gt(ga->gid[g], gb->gid[g]))
  			return 1;
  	}
  	return 0;
  }
  EXPORT_SYMBOL(cred_fscmp);

  /*
   * initialise the credentials stuff
   */
  void __init cred_init(void)
  {
  	/* allocate a slab in which we can store credentials */

  	cred_jar = kmem_cache_create("cred_jar", sizeof(struct cred), 0,
  			SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL);

  }

  
  /**
   * prepare_kernel_cred - Prepare a set of credentials for a kernel service
   * @daemon: A userspace daemon to be used as a reference
   *
   * Prepare a set of credentials for a kernel service.  This can then be used to
   * override a task's own credentials so that work can be done on behalf of that
   * task that requires a different subjective context.
   *
   * @daemon is used to provide a base for the security record, but can be NULL.
   * If @daemon is supplied, then the security data will be derived from that;
   * otherwise they'll be set to 0 and no groups, full capabilities and no keys.
   *
   * The caller may change these controls afterwards if desired.
   *
   * Returns the new credentials or NULL if out of memory.

   */
  struct cred *prepare_kernel_cred(struct task_struct *daemon)
  {
  	const struct cred *old;
  	struct cred *new;
  
  	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
  	if (!new)
  		return NULL;

  	kdebug("prepare_kernel_cred() alloc %p", new);

  	if (daemon)
  		old = get_task_cred(daemon);
  	else
  		old = get_cred(&init_cred);

  	validate_creds(old);

  	*new = *old;

  	new->non_rcu = 0;

  	atomic_set(&new->usage, 1);
  	set_cred_subscribers(new, 0);

  	get_uid(new->user);

  	get_user_ns(new->user_ns);

  	get_group_info(new->group_info);
  
  #ifdef CONFIG_KEYS

  	new->session_keyring = NULL;
  	new->process_keyring = NULL;

  	new->thread_keyring = NULL;

  	new->request_key_auth = NULL;

  	new->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
  #endif
  
  #ifdef CONFIG_SECURITY
  	new->security = NULL;
  #endif

  	if (security_prepare_creds(new, old, GFP_KERNEL_ACCOUNT) < 0)

  		goto error;

  	put_cred(old);

  	validate_creds(new);

  	return new;
  
  error:
  	put_cred(new);

  	put_cred(old);

  	return NULL;
  }
  EXPORT_SYMBOL(prepare_kernel_cred);
  
  /**
   * set_security_override - Set the security ID in a set of credentials
   * @new: The credentials to alter
   * @secid: The LSM security ID to set
   *
   * Set the LSM security ID in a set of credentials so that the subjective
   * security is overridden when an alternative set of credentials is used.
   */
  int set_security_override(struct cred *new, u32 secid)
  {
  	return security_kernel_act_as(new, secid);
  }
  EXPORT_SYMBOL(set_security_override);
  
  /**
   * set_security_override_from_ctx - Set the security ID in a set of credentials
   * @new: The credentials to alter
   * @secctx: The LSM security context to generate the security ID from.
   *
   * Set the LSM security ID in a set of credentials so that the subjective
   * security is overridden when an alternative set of credentials is used.  The
   * security ID is specified in string form as a security context to be
   * interpreted by the LSM.
   */
  int set_security_override_from_ctx(struct cred *new, const char *secctx)
  {
  	u32 secid;
  	int ret;
  
  	ret = security_secctx_to_secid(secctx, strlen(secctx), &secid);
  	if (ret < 0)
  		return ret;
  
  	return set_security_override(new, secid);
  }
  EXPORT_SYMBOL(set_security_override_from_ctx);
  
  /**
   * set_create_files_as - Set the LSM file create context in a set of credentials
   * @new: The credentials to alter
   * @inode: The inode to take the context from
   *
   * Change the LSM file creation context in a set of credentials to be the same
   * as the object context of the specified inode, so that the new inodes have
   * the same MAC context as that inode.
   */
  int set_create_files_as(struct cred *new, struct inode *inode)
  {

  	if (!uid_valid(inode->i_uid) || !gid_valid(inode->i_gid))
  		return -EINVAL;

  	new->fsuid = inode->i_uid;
  	new->fsgid = inode->i_gid;
  	return security_kernel_create_files_as(new, inode);
  }
  EXPORT_SYMBOL(set_create_files_as);

  
  #ifdef CONFIG_DEBUG_CREDENTIALS

  bool creds_are_invalid(const struct cred *cred)
  {
  	if (cred->magic != CRED_MAGIC)
  		return true;

  	return false;
  }

  EXPORT_SYMBOL(creds_are_invalid);

  /*
   * dump invalid credentials
   */
  static void dump_invalid_creds(const struct cred *cred, const char *label,
  			       const struct task_struct *tsk)
  {
  	printk(KERN_ERR "CRED: %s credentials: %p %s%s%s
  ",
  	       label, cred,
  	       cred == &init_cred ? "[init]" : "",
  	       cred == tsk->real_cred ? "[real]" : "",
  	       cred == tsk->cred ? "[eff]" : "");
  	printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p
  ",
  	       cred->magic, cred->put_addr);
  	printk(KERN_ERR "CRED: ->usage=%d, subscr=%d
  ",
  	       atomic_read(&cred->usage),
  	       read_cred_subscribers(cred));
  	printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }
  ",

  		from_kuid_munged(&init_user_ns, cred->uid),
  		from_kuid_munged(&init_user_ns, cred->euid),
  		from_kuid_munged(&init_user_ns, cred->suid),
  		from_kuid_munged(&init_user_ns, cred->fsuid));

  	printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }
  ",

  		from_kgid_munged(&init_user_ns, cred->gid),
  		from_kgid_munged(&init_user_ns, cred->egid),
  		from_kgid_munged(&init_user_ns, cred->sgid),
  		from_kgid_munged(&init_user_ns, cred->fsgid));

  #ifdef CONFIG_SECURITY
  	printk(KERN_ERR "CRED: ->security is %p
  ", cred->security);
  	if ((unsigned long) cred->security >= PAGE_SIZE &&
  	    (((unsigned long) cred->security & 0xffffff00) !=
  	     (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8)))
  		printk(KERN_ERR "CRED: ->security {%x, %x}
  ",
  		       ((u32*)cred->security)[0],
  		       ((u32*)cred->security)[1]);
  #endif
  }
  
  /*
   * report use of invalid credentials
   */
  void __invalid_creds(const struct cred *cred, const char *file, unsigned line)
  {
  	printk(KERN_ERR "CRED: Invalid credentials
  ");
  	printk(KERN_ERR "CRED: At %s:%u
  ", file, line);
  	dump_invalid_creds(cred, "Specified", current);
  	BUG();
  }
  EXPORT_SYMBOL(__invalid_creds);
  
  /*
   * check the credentials on a process
   */
  void __validate_process_creds(struct task_struct *tsk,
  			      const char *file, unsigned line)
  {
  	if (tsk->cred == tsk->real_cred) {
  		if (unlikely(read_cred_subscribers(tsk->cred) < 2 ||
  			     creds_are_invalid(tsk->cred)))
  			goto invalid_creds;
  	} else {
  		if (unlikely(read_cred_subscribers(tsk->real_cred) < 1 ||
  			     read_cred_subscribers(tsk->cred) < 1 ||
  			     creds_are_invalid(tsk->real_cred) ||
  			     creds_are_invalid(tsk->cred)))
  			goto invalid_creds;
  	}
  	return;
  
  invalid_creds:
  	printk(KERN_ERR "CRED: Invalid process credentials
  ");
  	printk(KERN_ERR "CRED: At %s:%u
  ", file, line);
  
  	dump_invalid_creds(tsk->real_cred, "Real", tsk);
  	if (tsk->cred != tsk->real_cred)
  		dump_invalid_creds(tsk->cred, "Effective", tsk);
  	else
  		printk(KERN_ERR "CRED: Effective creds == Real creds
  ");
  	BUG();
  }
  EXPORT_SYMBOL(__validate_process_creds);
  
  /*
   * check creds for do_exit()
   */
  void validate_creds_for_do_exit(struct task_struct *tsk)
  {
  	kdebug("validate_creds_for_do_exit(%p,%p{%d,%d})",
  	       tsk->real_cred, tsk->cred,
  	       atomic_read(&tsk->cred->usage),
  	       read_cred_subscribers(tsk->cred));
  
  	__validate_process_creds(tsk, __FILE__, __LINE__);
  }
  
  #endif /* CONFIG_DEBUG_CREDENTIALS */