rw_semaphore: remove up/down_read_non_owner
[linux-2.6.git] / kernel / cred.c
index 833244a..174fa84 100644 (file)
@@ -1,4 +1,4 @@
-/* Task credentials management
+/* Task credentials management - see Documentation/security/credentials.txt
  *
  * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells (dhowells@redhat.com)
  */
 #include <linux/module.h>
 #include <linux/cred.h>
+#include <linux/slab.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>
+
+#if 0
+#define kdebug(FMT, ...) \
+       printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
+#else
+#define kdebug(FMT, ...) \
+       no_printk("[%-5.5s%5u] "FMT"\n", current->comm, current->pid ,##__VA_ARGS__)
+#endif
+
+static struct kmem_cache *cred_jar;
+
+/*
+ * The common credentials for the initial task's thread group
+ */
+#ifdef CONFIG_KEYS
+static struct thread_group_cred init_tgcred = {
+       .usage  = ATOMIC_INIT(2),
+       .tgid   = 0,
+       .lock   = __SPIN_LOCK_UNLOCKED(init_cred.tgcred.lock),
+};
+#endif
 
 /*
  * 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_inheritable        = CAP_EMPTY_SET,
        .cap_permitted          = CAP_FULL_SET,
-       .cap_effective          = CAP_INIT_EFF_SET,
-       .cap_bset               = CAP_INIT_BSET,
+       .cap_effective          = CAP_FULL_SET,
+       .cap_bset               = CAP_FULL_SET,
        .user                   = INIT_USER,
+       .user_ns                = &init_user_ns,
        .group_info             = &init_groups,
+#ifdef CONFIG_KEYS
+       .tgcred                 = &init_tgcred,
+#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
+ */
+#ifdef CONFIG_KEYS
+static 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
  */
@@ -37,60 +123,739 @@ static void put_cred_rcu(struct rcu_head *rcu)
 {
        struct cred *cred = container_of(rcu, struct cred, rcu);
 
-       BUG_ON(atomic_read(&cred->usage) != 0);
+       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);
-       put_group_info(cred->group_info);
+       release_tgcred(cred);
+       if (cred->group_info)
+               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)
 {
+       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);
+       }
+}
+
+/**
+ * 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 (!atomic_inc_not_zero(&((struct cred *)cred)->usage));
+
+       rcu_read_unlock();
+       return 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);
+#ifdef CONFIG_DEBUG_CREDENTIALS
+       new->magic = CRED_MAGIC;
+#endif
+
+       if (security_cred_alloc_blank(new, GFP_KERNEL) < 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));
+
+       atomic_set(&new->usage, 1);
+       set_cred_subscribers(new, 0);
+       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;
+       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 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;
+}
+
+/*
  * 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)
+       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;
+       }
+
+       /* cache user_ns in cred.  Doesn't need a refcount because it will
+        * stay pinned by cred->user
+        */
+       new->user_ns = new->user->user_ns;
+
+#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);
+       alter_cred_subscribers(new, 2);
+       validate_creds(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 = 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 (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
+        */
+       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 (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)
+{
+       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);
+       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 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);
+
+/*
+ * 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;
+
+       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;
+       atomic_set(&new->usage, 1);
+       set_cred_subscribers(new, 0);
+       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
-       pcred->security = NULL;
+       new->security = NULL;
 #endif
+       if (security_prepare_creds(new, old, GFP_KERNEL) < 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_cred_alloc(pcred);
-       if (ret < 0) {
-               kfree(pcred);
+       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;
+#ifdef CONFIG_SECURITY_SELINUX
+       /*
+        * cred->security == NULL if security_cred_alloc_blank() or
+        * security_prepare_creds() returned an error.
+        */
+       if (selinux_is_enabled() && cred->security) {
+               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;
 
-       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);
+invalid_creds:
+       printk(KERN_ERR "CRED: Invalid process credentials\n");
+       printk(KERN_ERR "CRED: At %s:%u\n", file, line);
 
-       atomic_inc(&pcred->user->processes);
+       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);
 
-       /* RCU assignment is unneeded here as no-one can have accessed this
-        * pointer yet, barring us */
-       p->cred = pcred;
-       return 0;
+/*
+ * 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 */