1 files changed, 284 insertions, 37 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index ac73e3617684..cb6b5eda978d 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -15,6 +15,10 @@
 #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
@@ -64,7 +68,7 @@ static void release_tgcred_rcu(struct rcu_head *rcu)
 /*
  * Release a set of thread group credentials.
  */
-static void release_tgcred(struct cred *cred)
+void release_tgcred(struct cred *cred)
 {
 #ifdef CONFIG_KEYS
         struct thread_group_cred *tgcred = cred->tgcred;
@@ -81,79 +85,322 @@ 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);
+        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().
+ *
+ * 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->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 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.
  */
 int copy_creds(struct task_struct *p, unsigned long clone_flags)
 {
-        struct cred *pcred;
-        int ret;
+#ifdef CONFIG_KEYS
+        struct thread_group_cred *tgcred;
+#endif
+        struct cred *new;
+
+        mutex_init(&p->cred_exec_mutex);
 
-        pcred = kmemdup(p->cred, sizeof(*p->cred), GFP_KERNEL);
-        if (!pcred)
+        if (
+#ifdef CONFIG_KEYS
+                !p->cred->thread_keyring &&
+#endif
+                clone_flags & CLONE_THREAD
+            ) {
+                get_cred(p->cred);
+                atomic_inc(&p->cred->user->processes);
+                return 0;
+        }
+
+        new = prepare_creds();
+        if (!new)
                 return -ENOMEM;
 
 #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);
+        /* 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) {
+                        put_cred(new);
                         return -ENOMEM;
                 }
-                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 = new;
+        return 0;
+}
 
-        ret = security_cred_alloc(pcred);
-        if (ret < 0) {
-                release_tgcred(pcred);
-                kfree(pcred);
-                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.
+ *
+ * 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(atomic_read(&new->usage) < 1);
+        BUG_ON(atomic_read(&task->cred->usage) < 1);
+
+        old = task->cred;
+        security_commit_creds(new, old);
+
+        /* 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);
+                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->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;
+        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 - Temporarily override the current process's 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.
+ */
+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 credentials override
+ * @old: The credentials to be restored
+ *
+ * Revert a temporary set of override 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);
+}