1 files changed, 45 insertions, 1 deletions

diff --git a/kernel/cred.c b/kernel/cred.c
index cb6b5eda978d..e6fcdd67b2ec 100644
--- a/kernel/cred.c
+++ b/kernel/cred.c
@@ -68,7 +68,7 @@ static void release_tgcred_rcu(struct rcu_head *rcu)
 /*
  * 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;
@@ -164,6 +164,50 @@ error:
 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)