-/* Task credentials management
+/* Task credentials management - see Documentation/credentials.txt
*
* Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
* Written by David Howells (dhowells@redhat.com)
#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
* The initial credentials for the initial task
*/
struct cred init_cred = {
- .usage = ATOMIC_INIT(3),
+ .usage = ATOMIC_INIT(4),
.securebits = SECUREBITS_DEFAULT,
.cap_inheritable = CAP_INIT_INH_SET,
.cap_permitted = CAP_FULL_SET,
{
struct cred *cred = container_of(rcu, struct cred, rcu);
- BUG_ON(atomic_read(&cred->usage) != 0);
+ 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);
- security_cred_free(cred);
- kfree(cred);
+ kmem_cache_free(cred_jar, cred);
}
/**
* __put_cred - Destroy a set of credentials
- * @sec: The record to release
+ * @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)
{
- struct cred *pcred;
+#ifdef CONFIG_KEYS
+ struct thread_group_cred *tgcred;
+#endif
+ struct cred *new;
int ret;
- pcred = kmemdup(p->cred, sizeof(*p->cred), GFP_KERNEL);
- if (!pcred)
+ 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
- if (clone_flags & CLONE_THREAD) {
- atomic_inc(&pcred->tgcred->usage);
- } else {
- pcred->tgcred = kmalloc(sizeof(struct cred), GFP_KERNEL);
- if (!pcred->tgcred) {
- kfree(pcred);
- return -ENOMEM;
+ /* 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(&pcred->tgcred->usage, 1);
- spin_lock_init(&pcred->tgcred->lock);
- pcred->tgcred->process_keyring = NULL;
- pcred->tgcred->session_keyring =
- key_get(p->cred->tgcred->session_keyring);
+ 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
-#ifdef CONFIG_SECURITY
- pcred->security = NULL;
-#endif
+ atomic_inc(&new->user->processes);
+ p->cred = p->real_cred = get_cred(new);
+ return 0;
- ret = security_cred_alloc(pcred);
- if (ret < 0) {
- release_tgcred(pcred);
- kfree(pcred);
- return ret;
+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();
}
- atomic_set(&pcred->usage, 1);
- get_group_info(pcred->group_info);
- get_uid(pcred->user);
- key_get(pcred->thread_keyring);
- key_get(pcred->request_key_auth);
+ /* 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);
- atomic_inc(&pcred->user->processes);
+ if (new->gid != old->gid ||
+ new->egid != old->egid ||
+ new->sgid != old->sgid ||
+ new->fsgid != old->fsgid)
+ proc_id_connector(task, PROC_EVENT_GID);
- /* RCU assignment is unneeded here as no-one can have accessed this
- * pointer yet, barring us */
- p->cred = pcred;
+ /* 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;
+
+ new = kmem_cache_alloc(cred_jar, GFP_KERNEL);
+ if (!new)
+ return NULL;
+
+ if (daemon)
+ old = get_task_cred(daemon);
+ else
+ old = get_cred(&init_cred);
+
+ *new = *old;
+ get_uid(new->user);
+ get_group_info(new->group_info);
+
+#ifdef CONFIG_KEYS
+ atomic_inc(&init_tgcred.usage);
+ new->tgcred = &init_tgcred;
+ new->request_key_auth = NULL;
+ new->thread_keyring = 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) < 0)
+ goto error;
+
+ atomic_set(&new->usage, 1);
+ put_cred(old);
+ 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)
+{
+ new->fsuid = inode->i_uid;
+ new->fsgid = inode->i_gid;
+ return security_kernel_create_files_as(new, inode);
+}
+EXPORT_SYMBOL(set_create_files_as);
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff