/* Task credentials management - see Documentation/credentials.txt * * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved. * Written by David Howells (dhowells@redhat.com) * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public Licence * as published by the Free Software Foundation; either version * 2 of the Licence, or (at your option) any later version. */#include <linux/module.h>#include <linux/cred.h>#include <linux/sched.h>#include <linux/key.h>#include <linux/keyctl.h>#include <linux/init_task.h>#include <linux/security.h>#include <linux/cn_proc.h>#include "cred-internals.h" static struct kmem_cache *cred_jar; /* * The common credentials for the initial task's thread group */#ifdef CONFIG_KEYSstatic struct thread_group_cred init_tgcred = {	.usage	= ATOMIC_INIT(2),	.tgid	= 0,	.lock	= SPIN_LOCK_UNLOCKED,};#endif /* * The initial credentials for the initial task */struct cred init_cred = {	.usage			= ATOMIC_INIT(4),	.securebits		= SECUREBITS_DEFAULT,	.cap_inheritable	= CAP_INIT_INH_SET,	.cap_permitted		= CAP_FULL_SET,	.cap_effective		= CAP_INIT_EFF_SET,	.cap_bset		= CAP_INIT_BSET,	.user			= INIT_USER,	.group_info		= &init_groups,#ifdef CONFIG_KEYS	.tgcred			= &init_tgcred,#endif}; /* * Dispose of the shared task group credentials */#ifdef CONFIG_KEYSstatic void release_tgcred_rcu(struct rcu_head *rcu){	struct thread_group_cred *tgcred =		container_of(rcu, struct thread_group_cred, rcu); 	BUG_ON(atomic_read(&tgcred->usage) != 0); 	key_put(tgcred->session_keyring);	key_put(tgcred->process_keyring);	kfree(tgcred);}#endif /* * Release a set of thread group credentials. */static void release_tgcred(struct cred *cred){#ifdef CONFIG_KEYS	struct thread_group_cred *tgcred = cred->tgcred; 	if (atomic_dec_and_test(&tgcred->usage))		call_rcu(&tgcred->rcu, release_tgcred_rcu);#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); 	if (atomic_read(&cred->usage) != 0)		panic("CRED: put_cred_rcu() sees %p with usage %d\n",		      cred, atomic_read(&cred->usage)); 	security_cred_free(cred);	key_put(cred->thread_keyring);	key_put(cred->request_key_auth);	release_tgcred(cred);	put_group_info(cred->group_info);	free_uid(cred->user);	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){	BUG_ON(atomic_read(&cred->usage) != 0); 	call_rcu(&cred->rcu, put_cred_rcu);}EXPORT_SYMBOL(__put_cred); /** * 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; 	BUG_ON(atomic_read(&task->real_cred->usage) < 1); 	new = kmem_cache_alloc(cred_jar, GFP_KERNEL);	if (!new)		return NULL; 	old = task->cred;	memcpy(new, old, sizeof(struct cred)); 	atomic_set(&new->usage, 1);	get_group_info(new->group_info);	get_uid(new->user); #ifdef CONFIG_KEYS	key_get(new->thread_keyring);	key_get(new->request_key_auth);	atomic_inc(&new->tgcred->usage);#endif #ifdef CONFIG_SECURITY	new->security = NULL;#endif 	if (security_prepare_creds(new, old, GFP_KERNEL) < 0)		goto error;	return new; error:	abort_creds(new);	return NULL;}EXPORT_SYMBOL(prepare_creds); /* * Prepare credentials for current to perform an execve() * - The caller must hold current->cred_exec_mutex */struct cred *prepare_exec_creds(void){	struct thread_group_cred *tgcred = NULL;	struct cred *new; #ifdef CONFIG_KEYS	tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);	if (!tgcred)		return NULL;#endif 	new = prepare_creds();	if (!new) {		kfree(tgcred);		return new;	} #ifdef CONFIG_KEYS	/* newly exec'd tasks don't get a thread keyring */	key_put(new->thread_keyring);	new->thread_keyring = NULL; 	/* create a new per-thread-group creds for all this set of threads to	 * share */	memcpy(tgcred, new->tgcred, sizeof(struct thread_group_cred)); 	atomic_set(&tgcred->usage, 1);	spin_lock_init(&tgcred->lock); 	/* inherit the session keyring; new process keyring */	key_get(tgcred->session_keyring);	tgcred->process_keyring = NULL; 	release_tgcred(new);	new->tgcred = tgcred;#endif 	return new;} /* * prepare new credentials for the usermode helper dispatcher */struct cred *prepare_usermodehelper_creds(void){#ifdef CONFIG_KEYS	struct thread_group_cred *tgcred = NULL;#endif	struct cred *new; #ifdef CONFIG_KEYS	tgcred = kzalloc(sizeof(*new->tgcred), GFP_ATOMIC);	if (!tgcred)		return NULL;#endif 	new = kmem_cache_alloc(cred_jar, GFP_ATOMIC);	if (!new)		return NULL; 	memcpy(new, &init_cred, sizeof(struct cred)); 	atomic_set(&new->usage, 1);	get_group_info(new->group_info);	get_uid(new->user); #ifdef CONFIG_KEYS	new->thread_keyring = NULL;	new->request_key_auth = NULL;	new->jit_keyring = KEY_REQKEY_DEFL_DEFAULT; 	atomic_set(&tgcred->usage, 1);	spin_lock_init(&tgcred->lock);	new->tgcred = tgcred;#endif #ifdef CONFIG_SECURITY	new->security = NULL;#endif	if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)		goto error; 	BUG_ON(atomic_read(&new->usage) != 1);	return new; error:	put_cred(new);	return NULL;} /* * 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){#ifdef CONFIG_KEYS	struct thread_group_cred *tgcred;#endif	struct cred *new;	int ret; 	mutex_init(&p->cred_exec_mutex); 	if (#ifdef CONFIG_KEYS		!p->cred->thread_keyring &&#endif		clone_flags & CLONE_THREAD	    ) {		p->real_cred = get_cred(p->cred);		get_cred(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);	} 	/* we share the process and session keyrings between all the threads in	 * a process - this is slightly icky as we violate COW credentials a	 * bit */	if (!(clone_flags & CLONE_THREAD)) {		tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);		if (!tgcred) {			ret = -ENOMEM;			goto error_put;		}		atomic_set(&tgcred->usage, 1);		spin_lock_init(&tgcred->lock);		tgcred->process_keyring = NULL;		tgcred->session_keyring = key_get(new->tgcred->session_keyring); 		release_tgcred(new);		new->tgcred = tgcred;	}#endif 	atomic_inc(&new->user->processes);	p->cred = p->real_cred = get_cred(new);	return 0; error_put:	put_cred(new);	return ret;} /** * 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; 	BUG_ON(task->cred != task->real_cred);	BUG_ON(atomic_read(&task->real_cred->usage) < 2);	BUG_ON(atomic_read(&new->usage) < 1); 	old = task->real_cred;	security_commit_creds(new, old); 	get_cred(new); /* we will require a ref for the subj creds too */ 	/* dumpability changes */	if (old->euid != new->euid ||	    old->egid != new->egid ||	    old->fsuid != new->fsuid ||	    old->fsgid != new->fsgid ||	    !cap_issubset(new->cap_permitted, old->cap_permitted)) {		if (task->mm)			set_dumpable(task->mm, suid_dumpable);		task->pdeath_signal = 0;		smp_wmb();	} 	/* alter the thread keyring */	if (new->fsuid != old->fsuid)		key_fsuid_changed(task);	if (new->fsgid != old->fsgid)		key_fsgid_changed(task); 	/* do it	 * - What if a process setreuid()'s and this brings the	 *   new uid over his NPROC rlimit?  We can check this now	 *   cheaply with the new uid cache, so if it matters	 *   we should be checking for it.  -DaveM	 */	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); 	sched_switch_user(task); 	/* send notifications */	if (new->uid   != old->uid  ||	    new->euid  != old->euid ||	    new->suid  != old->suid ||	    new->fsuid != old->fsuid)		proc_id_connector(task, PROC_EVENT_UID); 	if (new->gid   != old->gid  ||	    new->egid  != old->egid ||	    new->sgid  != old->sgid ||	    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){	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; 	rcu_assign_pointer(current->cred, get_cred(new));	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; 	rcu_assign_pointer(current->cred, old);	put_cred(override);}EXPORT_SYMBOL(revert_creds); /* * 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, 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. * * Does not take, and does not return holding current->cred_replace_mutex. */struct cred *prepare_kernel_cred(struct task_struct *daemon){	const struct cred *old;	struct cred *new; 

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