merge task_work and rcu_head, get rid of separate allocation for keyring case

task_work and rcu_head are identical now; merge them (calling the result
struct callback_head, rcu_head #define'd to it), kill separate allocation
in security/keys since we can just use cred->rcu now.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

3 files changed, 12 insertions, 28 deletions

diff --git a/security/keys/internal.h b/security/keys/internal.h
index b510a316874a..c246ba5d43ab 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -148,12 +148,8 @@ extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
 #define KEY_LOOKUP_PARTIAL      0x02
 #define KEY_LOOKUP_FOR_UNLINK   0x04
 
-struct kludge { /* this will die off very soon */
-        struct task_work twork;
-        struct cred *cred;
-};
 extern long join_session_keyring(const char *name);
-extern void key_change_session_keyring(struct task_work *twork);
+extern void key_change_session_keyring(struct callback_head *twork);
 
 extern struct work_struct key_gc_work;
 extern unsigned key_gc_delay;
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 26723caaad05..0291b3f9397c 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1456,8 +1456,7 @@ long keyctl_session_to_parent(void)
 {
         struct task_struct *me, *parent;
         const struct cred *mycred, *pcred;
-        struct kludge *newwork;
-        struct task_work *oldwork;
+        struct callback_head *newwork, *oldwork;
         key_ref_t keyring_r;
         struct cred *cred;
         int ret;
@@ -1467,20 +1466,17 @@ long keyctl_session_to_parent(void)
                 return PTR_ERR(keyring_r);
 
         ret = -ENOMEM;
-        newwork = kmalloc(sizeof(struct kludge), GFP_KERNEL);
-        if (!newwork)
-                goto error_keyring;
 
         /* our parent is going to need a new cred struct, a new tgcred struct
          * and new security data, so we allocate them here to prevent ENOMEM in
          * our parent */
         cred = cred_alloc_blank();
         if (!cred)
-                goto error_newwork;
+                goto error_keyring;
+        newwork = &cred->rcu;
 
         cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
-        init_task_work(&newwork->twork, key_change_session_keyring);
-        newwork->cred = cred;
+        init_task_work(newwork, key_change_session_keyring);
 
         me = current;
         rcu_read_lock();
@@ -1529,24 +1525,18 @@ long keyctl_session_to_parent(void)
 
         /* the replacement session keyring is applied just prior to userspace
          * restarting */
-        ret = task_work_add(parent, &newwork->twork, true);
+        ret = task_work_add(parent, newwork, true);
         if (!ret)
                 newwork = NULL;
 unlock:
         write_unlock_irq(&tasklist_lock);
         rcu_read_unlock();
-        if (oldwork) {
-                put_cred(container_of(oldwork, struct kludge, twork)->cred);
-                kfree(oldwork);
-        }
-        if (newwork) {
-                put_cred(newwork->cred);
-                kfree(newwork);
-        }
+        if (oldwork)
+                put_cred(container_of(oldwork, struct cred, rcu));
+        if (newwork)
+                put_cred(cred);
         return ret;
 
-error_newwork:
-        kfree(newwork);
 error_keyring:
         key_ref_put(keyring_r);
         return ret;
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index c9b07c97d7f2..54339cfd6734 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -834,13 +834,11 @@ error:
  * Replace a process's session keyring on behalf of one of its children when
  * the target  process is about to resume userspace execution.
  */
-void key_change_session_keyring(struct task_work *twork)
+void key_change_session_keyring(struct callback_head *twork)
 {
         const struct cred *old = current_cred();
-        struct kludge *p = container_of(twork, struct kludge, twork);
-        struct cred *new = p->cred;
+        struct cred *new = container_of(twork, struct cred, rcu);
 
-        kfree(p);
         if (unlikely(current->flags & PF_EXITING)) {
                 put_cred(new);
                 return;