-/* 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/cn_proc.h>
#include "cred-internals.h"
+#if 0
+#define kdebug(FMT, ...) \
+ printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
+#else
+static inline __attribute__((format(printf, 1, 2)))
+void no_printk(const char *fmt, ...)
+{
+}
+#define kdebug(FMT, ...) \
+ no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
+#endif
+
static struct kmem_cache *cred_jar;
/*
* The initial credentials for the initial task
*/
struct cred init_cred = {
- .usage = ATOMIC_INIT(3),
+ .usage = ATOMIC_INIT(4),
+#ifdef CONFIG_DEBUG_CREDENTIALS
+ .subscribers = ATOMIC_INIT(2),
+ .magic = CRED_MAGIC,
+#endif
.securebits = SECUREBITS_DEFAULT,
.cap_inheritable = CAP_INIT_INH_SET,
.cap_permitted = CAP_FULL_SET,
#endif
};
+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
+}
+
/*
* Dispose of the shared task group credentials
*/
/*
* Release a set of thread group credentials.
*/
-void release_tgcred(struct cred *cred)
+static void release_tgcred(struct cred *cred)
{
#ifdef CONFIG_KEYS
struct thread_group_cred *tgcred = cred->tgcred;
{
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\n",
+ 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\n",
cred, atomic_read(&cred->usage));
+#endif
security_cred_free(cred);
key_put(cred->thread_keyring);
key_put(cred->request_key_auth);
release_tgcred(cred);
- put_group_info(cred->group_info);
+ if (cred->group_info)
+ put_group_info(cred->group_info);
free_uid(cred->user);
kmem_cache_free(cred_jar, cred);
}
*/
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);
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);
+
+ cred = (struct cred *) tsk->replacement_session_keyring;
+ if (cred) {
+ tsk->replacement_session_keyring = NULL;
+ validate_creds(cred);
+ put_cred(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;
+
+#ifdef CONFIG_KEYS
+ new->tgcred = kzalloc(sizeof(*new->tgcred), GFP_KERNEL);
+ if (!new->tgcred) {
+ kmem_cache_free(cred_jar, new);
+ return NULL;
+ }
+ atomic_set(&new->tgcred->usage, 1);
+#endif
+
+ atomic_set(&new->usage, 1);
+
+ if (security_cred_alloc_blank(new, GFP_KERNEL) < 0)
+ goto error;
+
+#ifdef CONFIG_DEBUG_CREDENTIALS
+ new->magic = CRED_MAGIC;
+#endif
+ return new;
+
+error:
+ abort_creds(new);
+ return NULL;
+}
+
/**
* prepare_creds - Prepare a new set of credentials for modification
*
* 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.
const struct cred *old;
struct cred *new;
- BUG_ON(atomic_read(&task->cred->usage) < 1);
+ 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));
atomic_set(&new->usage, 1);
+ set_cred_subscribers(new, 0);
get_group_info(new->group_info);
get_uid(new->user);
if (security_prepare_creds(new, old, GFP_KERNEL) < 0)
goto error;
+ validate_creds(new);
return new;
error:
EXPORT_SYMBOL(prepare_creds);
/*
+ * Prepare credentials for current to perform an execve()
+ * - The caller must hold current->cred_guard_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)
if (!new)
return NULL;
+ kdebug("prepare_usermodehelper_creds() alloc %p", new);
+
memcpy(new, &init_cred, sizeof(struct cred));
atomic_set(&new->usage, 1);
+ set_cred_subscribers(new, 0);
get_group_info(new->group_info);
get_uid(new->user);
#endif
if (security_prepare_creds(new, &init_cred, GFP_ATOMIC) < 0)
goto error;
+ validate_creds(new);
BUG_ON(atomic_read(&new->usage) != 1);
return new;
*
* 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 thread_group_cred *tgcred;
#endif
struct cred *new;
+ int ret;
- mutex_init(&p->cred_exec_mutex);
+ mutex_init(&p->cred_guard_mutex);
if (
#ifdef CONFIG_KEYS
#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;
}
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 (!(clone_flags & CLONE_THREAD)) {
tgcred = kmalloc(sizeof(*tgcred), GFP_KERNEL);
if (!tgcred) {
- put_cred(new);
- return -ENOMEM;
+ ret = -ENOMEM;
+ goto error_put;
}
atomic_set(&tgcred->usage, 1);
spin_lock_init(&tgcred->lock);
#endif
atomic_inc(&new->user->processes);
- p->cred = new;
+ 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;
}
/**
* @new: The credentials to be assigned
*
* Install a new set of credentials to the current task, using RCU to replace
- * the old set.
+ * 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.
*
int commit_creds(struct cred *new)
{
struct task_struct *task = current;
- const struct cred *old;
+ 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);
- BUG_ON(atomic_read(&task->cred->usage) < 1);
- old = task->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)) {
- set_dumpable(task->mm, suid_dumpable);
+ if (task->mm)
+ set_dumpable(task->mm, suid_dumpable);
task->pdeath_signal = 0;
smp_wmb();
}
* cheaply with the new uid cache, so if it matters
* we should be checking for it. -DaveM
*/
+ 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);
sched_switch_user(task);
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;
}
*/
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 - Temporarily override the current process's credentials
+ * override_creds - Override the current process's subjective credentials
* @new: The credentials to be assigned
*
- * Install a set of temporary override credentials on the current process,
- * returning the old set for later reversion.
+ * 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));
+ kdebug("override_creds(%p{%d,%d})", new,
+ atomic_read(&new->usage),
+ read_cred_subscribers(new));
+
+ validate_creds(old);
+ validate_creds(new);
+ get_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 credentials override
+ * revert_creds - Revert a temporary subjective credentials override
* @old: The credentials to be restored
*
- * Revert a temporary set of override credentials to an old set, discarding the
- * override set.
+ * 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_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;
+
+ 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;
+ 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);
+ set_cred_subscribers(new, 0);
+ 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)
+{
+ 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;
+ if (atomic_read(&cred->usage) < atomic_read(&cred->subscribers))
+ return true;
+#ifdef CONFIG_SECURITY_SELINUX
+ if (selinux_is_enabled()) {
+ if ((unsigned long) cred->security < PAGE_SIZE)
+ return true;
+ if ((*(u32 *)cred->security & 0xffffff00) ==
+ (POISON_FREE << 24 | POISON_FREE << 16 | POISON_FREE << 8))
+ return true;
+ }
+#endif
+ 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\n",
+ label, cred,
+ cred == &init_cred ? "[init]" : "",
+ cred == tsk->real_cred ? "[real]" : "",
+ cred == tsk->cred ? "[eff]" : "");
+ printk(KERN_ERR "CRED: ->magic=%x, put_addr=%p\n",
+ cred->magic, cred->put_addr);
+ printk(KERN_ERR "CRED: ->usage=%d, subscr=%d\n",
+ atomic_read(&cred->usage),
+ read_cred_subscribers(cred));
+ printk(KERN_ERR "CRED: ->*uid = { %d,%d,%d,%d }\n",
+ cred->uid, cred->euid, cred->suid, cred->fsuid);
+ printk(KERN_ERR "CRED: ->*gid = { %d,%d,%d,%d }\n",
+ cred->gid, cred->egid, cred->sgid, cred->fsgid);
+#ifdef CONFIG_SECURITY
+ printk(KERN_ERR "CRED: ->security is %p\n", 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}\n",
+ ((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\n");
+ printk(KERN_ERR "CRED: At %s:%u\n", 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\n");
+ printk(KERN_ERR "CRED: At %s:%u\n", 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\n");
+ 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 */
git://ftp.safe.ca / safe / jmp / linux-2.6 / blobdiff