CRED: Separate per-task-group keyrings from signal_struct

Separate per-task-group keyrings from signal_struct and dangle their anchor
from the cred struct rather than the signal_struct.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: James Morris <jmorris@namei.org>
Signed-off-by: James Morris <jmorris@namei.org>

1 files changed, 40 insertions, 60 deletions

diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index 212601ebaa46..70ee93406f30 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -189,7 +189,7 @@ int install_process_keyring(void)
 
         might_sleep();
 
-        if (!tsk->signal->process_keyring) {
+        if (!tsk->cred->tgcred->process_keyring) {
                 sprintf(buf, "_pid.%u", tsk->tgid);
 
                 keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk,
@@ -200,12 +200,12 @@ int install_process_keyring(void)
                 }
 
                 /* attach keyring */
-                spin_lock_irq(&tsk->sighand->siglock);
-                if (!tsk->signal->process_keyring) {
-                        tsk->signal->process_keyring = keyring;
+                spin_lock_irq(&tsk->cred->tgcred->lock);
+                if (!tsk->cred->tgcred->process_keyring) {
+                        tsk->cred->tgcred->process_keyring = keyring;
                         keyring = NULL;
                 }
-                spin_unlock_irq(&tsk->sighand->siglock);
+                spin_unlock_irq(&tsk->cred->tgcred->lock);
 
                 key_put(keyring);
         }
@@ -235,11 +235,11 @@ static int install_session_keyring(struct key *keyring)
                 sprintf(buf, "_ses.%u", tsk->tgid);
 
                 flags = KEY_ALLOC_QUOTA_OVERRUN;
-                if (tsk->signal->session_keyring)
+                if (tsk->cred->tgcred->session_keyring)
                         flags = KEY_ALLOC_IN_QUOTA;
 
-                keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid, tsk,
-                                        flags, NULL);
+                keyring = keyring_alloc(buf, tsk->cred->uid, tsk->cred->gid,
+                                        tsk, flags, NULL);
                 if (IS_ERR(keyring))
                         return PTR_ERR(keyring);
         }
@@ -248,10 +248,10 @@ static int install_session_keyring(struct key *keyring)
         }
 
         /* install the keyring */
-        spin_lock_irq(&tsk->sighand->siglock);
-        old = tsk->signal->session_keyring;
-        rcu_assign_pointer(tsk->signal->session_keyring, keyring);
-        spin_unlock_irq(&tsk->sighand->siglock);
+        spin_lock_irq(&tsk->cred->tgcred->lock);
+        old = tsk->cred->tgcred->session_keyring;
+        rcu_assign_pointer(tsk->cred->tgcred->session_keyring, keyring);
+        spin_unlock_irq(&tsk->cred->tgcred->lock);
 
         /* we're using RCU on the pointer, but there's no point synchronising
          * on it if it didn't previously point to anything */
@@ -266,28 +266,6 @@ static int install_session_keyring(struct key *keyring)
 
 /*****************************************************************************/
 /*
- * copy the keys in a thread group for fork without CLONE_THREAD
- */
-int copy_thread_group_keys(struct task_struct *tsk)
-{
-        key_check(current->thread_group->session_keyring);
-        key_check(current->thread_group->process_keyring);
-
-        /* no process keyring yet */
-        tsk->signal->process_keyring = NULL;
-
-        /* same session keyring */
-        rcu_read_lock();
-        tsk->signal->session_keyring =
-                key_get(rcu_dereference(current->signal->session_keyring));
-        rcu_read_unlock();
-
-        return 0;
-
-} /* end copy_thread_group_keys() */
-
-/*****************************************************************************/
-/*
  * copy the keys for fork
  */
 int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
@@ -307,17 +285,6 @@ int copy_keys(unsigned long clone_flags, struct task_struct *tsk)
 
 /*****************************************************************************/
 /*
- * dispose of thread group keys upon thread group destruction
- */
-void exit_thread_group_keys(struct signal_struct *tg)
-{
-        key_put(tg->session_keyring);
-        key_put(tg->process_keyring);
-
-} /* end exit_thread_group_keys() */
-
-/*****************************************************************************/
-/*
  * dispose of per-thread keys upon thread exit
  */
 void exit_keys(struct task_struct *tsk)
@@ -344,10 +311,10 @@ int exec_keys(struct task_struct *tsk)
         key_put(old);
 
         /* discard the process keyring from a newly exec'd task */
-        spin_lock_irq(&tsk->sighand->siglock);
-        old = tsk->signal->process_keyring;
-        tsk->signal->process_keyring = NULL;
-        spin_unlock_irq(&tsk->sighand->siglock);
+        spin_lock_irq(&tsk->cred->tgcred->lock);
+        old = tsk->cred->tgcred->process_keyring;
+        tsk->cred->tgcred->process_keyring = NULL;
+        spin_unlock_irq(&tsk->cred->tgcred->lock);
 
         key_put(old);
 
@@ -452,9 +419,9 @@ key_ref_t search_process_keyrings(struct key_type *type,
         }
 
         /* search the process keyring second */
-        if (context->signal->process_keyring) {
+        if (cred->tgcred->process_keyring) {
                 key_ref = keyring_search_aux(
-                        make_key_ref(context->signal->process_keyring, 1),
+                        make_key_ref(cred->tgcred->process_keyring, 1),
                         context, type, description, match);
                 if (!IS_ERR(key_ref))
                         goto found;
@@ -473,11 +440,11 @@ key_ref_t search_process_keyrings(struct key_type *type,
         }
 
         /* search the session keyring */
-        if (context->signal->session_keyring) {
+        if (cred->tgcred->session_keyring) {
                 rcu_read_lock();
                 key_ref = keyring_search_aux(
                         make_key_ref(rcu_dereference(
-                                             context->signal->session_keyring),
+                                             cred->tgcred->session_keyring),
                                      1),
                         context, type, description, match);
                 rcu_read_unlock();
@@ -586,11 +553,13 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
 {
         struct request_key_auth *rka;
         struct task_struct *t = current;
-        struct cred *cred = current_cred();
+        struct cred *cred;
         struct key *key;
         key_ref_t key_ref, skey_ref;
         int ret;
 
+try_again:
+        cred = get_current_cred();
         key_ref = ERR_PTR(-ENOKEY);
 
         switch (id) {
@@ -604,6 +573,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
                                 key = ERR_PTR(ret);
                                 goto error;
                         }
+                        goto reget_creds;
                 }
 
                 key = cred->thread_keyring;
@@ -612,7 +582,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
                 break;
 
         case KEY_SPEC_PROCESS_KEYRING:
-                if (!t->signal->process_keyring) {
+                if (!cred->tgcred->process_keyring) {
                         if (!create)
                                 goto error;
 
@@ -621,15 +591,16 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
                                 key = ERR_PTR(ret);
                                 goto error;
                         }
+                        goto reget_creds;
                 }
 
-                key = t->signal->process_keyring;
+                key = cred->tgcred->process_keyring;
                 atomic_inc(&key->usage);
                 key_ref = make_key_ref(key, 1);
                 break;
 
         case KEY_SPEC_SESSION_KEYRING:
-                if (!t->signal->session_keyring) {
+                if (!cred->tgcred->session_keyring) {
                         /* always install a session keyring upon access if one
                          * doesn't exist yet */
                         ret = install_user_keyrings();
@@ -639,10 +610,11 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
                                 cred->user->session_keyring);
                         if (ret < 0)
                                 goto error;
+                        goto reget_creds;
                 }
 
                 rcu_read_lock();
-                key = rcu_dereference(t->signal->session_keyring);
+                key = rcu_dereference(cred->tgcred->session_keyring);
                 atomic_inc(&key->usage);
                 rcu_read_unlock();
                 key_ref = make_key_ref(key, 1);
@@ -758,6 +730,7 @@ key_ref_t lookup_user_key(key_serial_t id, int create, int partial,
                 goto invalid_key;
 
 error:
+        put_cred(cred);
         return key_ref;
 
 invalid_key:
@@ -765,6 +738,12 @@ invalid_key:
         key_ref = ERR_PTR(ret);
         goto error;
 
+        /* if we attempted to install a keyring, then it may have caused new
+         * creds to be installed */
+reget_creds:
+        put_cred(cred);
+        goto try_again;
+
 } /* end lookup_user_key() */
 
 /*****************************************************************************/
@@ -777,6 +756,7 @@ invalid_key:
 long join_session_keyring(const char *name)
 {
         struct task_struct *tsk = current;
+        struct cred *cred = current->cred;
         struct key *keyring;
         long ret;
 
@@ -787,7 +767,7 @@ long join_session_keyring(const char *name)
                         goto error;
 
                 rcu_read_lock();
-                ret = rcu_dereference(tsk->signal->session_keyring)->serial;
+                ret = rcu_dereference(cred->tgcred->session_keyring)->serial;
                 rcu_read_unlock();
                 goto error;
         }
@@ -799,7 +779,7 @@ long join_session_keyring(const char *name)
         keyring = find_keyring_by_name(name, false);
         if (PTR_ERR(keyring) == -ENOKEY) {
                 /* not found - try and create a new one */
-                keyring = keyring_alloc(name, tsk->cred->uid, tsk->cred->gid, tsk,
+                keyring = keyring_alloc(name, cred->uid, cred->gid, tsk,
                                         KEY_ALLOC_IN_QUOTA, NULL);
                 if (IS_ERR(keyring)) {
                         ret = PTR_ERR(keyring);