Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal

Pull second pile of signal handling patches from Al Viro:
 "This one is just task_work_add() series + remaining prereqs for it.

  There probably will be another pull request from that tree this
  cycle - at least for helpers, to get them out of the way for per-arch
  fixes remaining in the tree."

Fix trivial conflict in kernel/irq/manage.c: the merge of Andrew's pile
had brought in commit 97fd75b7b8e0 ("kernel/irq/manage.c: use the
pr_foo() infrastructure to prefix printks") which changed one of the
pr_err() calls that this merge moves around.

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/signal:
  keys: kill task_struct->replacement_session_keyring
  keys: kill the dummy key_replace_session_keyring()
  keys: change keyctl_session_to_parent() to use task_work_add()
  genirq: reimplement exit_irq_thread() hook via task_work_add()
  task_work_add: generic process-context callbacks
  avr32: missed _TIF_NOTIFY_RESUME on one of do_notify_resume callers
  parisc: need to check NOTIFY_RESUME when exiting from syscall
  move key_repace_session_keyring() into tracehook_notify_resume()
  TIF_NOTIFY_RESUME is defined on all targets now

3 files changed, 44 insertions, 51 deletions

diff --git a/security/keys/internal.h b/security/keys/internal.h
index f711b094ed41..3dcbf86b0d31 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -14,6 +14,7 @@
 
 #include <linux/sched.h>
 #include <linux/key-type.h>
+#include <linux/task_work.h>
 
 #ifdef __KDEBUG
 #define kenter(FMT, ...) \
@@ -148,6 +149,7 @@ extern key_ref_t lookup_user_key(key_serial_t id, unsigned long flags,
 #define KEY_LOOKUP_FOR_UNLINK   0x04
 
 extern long join_session_keyring(const char *name);
+extern void key_change_session_keyring(struct task_work *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 21907ea35b15..0f5b3f027299 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -1454,50 +1454,57 @@ long keyctl_get_security(key_serial_t keyid,
  */
 long keyctl_session_to_parent(void)
 {
-#ifdef TIF_NOTIFY_RESUME
         struct task_struct *me, *parent;
         const struct cred *mycred, *pcred;
-        struct cred *cred, *oldcred;
+        struct task_work *newwork, *oldwork;
         key_ref_t keyring_r;
+        struct cred *cred;
         int ret;
 
         keyring_r = lookup_user_key(KEY_SPEC_SESSION_KEYRING, 0, KEY_LINK);
         if (IS_ERR(keyring_r))
                 return PTR_ERR(keyring_r);
 
+        ret = -ENOMEM;
+        newwork = kmalloc(sizeof(struct task_work), 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 */
-        ret = -ENOMEM;
         cred = cred_alloc_blank();
         if (!cred)
-                goto error_keyring;
+                goto error_newwork;
 
         cred->tgcred->session_keyring = key_ref_to_ptr(keyring_r);
-        keyring_r = NULL;
+        init_task_work(newwork, key_change_session_keyring, cred);
 
         me = current;
         rcu_read_lock();
         write_lock_irq(&tasklist_lock);
 
-        parent = me->real_parent;
         ret = -EPERM;
+        oldwork = NULL;
+        parent = me->real_parent;
 
         /* the parent mustn't be init and mustn't be a kernel thread */
         if (parent->pid <= 1 || !parent->mm)
-                goto not_permitted;
+                goto unlock;
 
         /* the parent must be single threaded */
         if (!thread_group_empty(parent))
-                goto not_permitted;
+                goto unlock;
 
         /* the parent and the child must have different session keyrings or
          * there's no point */
         mycred = current_cred();
         pcred = __task_cred(parent);
         if (mycred == pcred ||
-            mycred->tgcred->session_keyring == pcred->tgcred->session_keyring)
-                goto already_same;
+            mycred->tgcred->session_keyring == pcred->tgcred->session_keyring) {
+                ret = 0;
+                goto unlock;
+        }
 
         /* the parent must have the same effective ownership and mustn't be
          * SUID/SGID */
@@ -1507,50 +1514,40 @@ long keyctl_session_to_parent(void)
             pcred->gid  != mycred->egid ||
             pcred->egid != mycred->egid ||
             pcred->sgid != mycred->egid)
-                goto not_permitted;
+                goto unlock;
 
         /* the keyrings must have the same UID */
         if ((pcred->tgcred->session_keyring &&
              pcred->tgcred->session_keyring->uid != mycred->euid) ||
             mycred->tgcred->session_keyring->uid != mycred->euid)
-                goto not_permitted;
+                goto unlock;
 
-        /* if there's an already pending keyring replacement, then we replace
-         * that */
-        oldcred = parent->replacement_session_keyring;
+        /* cancel an already pending keyring replacement */
+        oldwork = task_work_cancel(parent, key_change_session_keyring);
 
         /* the replacement session keyring is applied just prior to userspace
          * restarting */
-        parent->replacement_session_keyring = cred;
-        cred = NULL;
-        set_ti_thread_flag(task_thread_info(parent), TIF_NOTIFY_RESUME);
-
+        ret = task_work_add(parent, newwork, true);
+        if (!ret)
+                newwork = NULL;
+unlock:
         write_unlock_irq(&tasklist_lock);
         rcu_read_unlock();
-        if (oldcred)
-                put_cred(oldcred);
-        return 0;
-
-already_same:
-        ret = 0;
-not_permitted:
-        write_unlock_irq(&tasklist_lock);
-        rcu_read_unlock();
-        put_cred(cred);
+        if (oldwork) {
+                put_cred(oldwork->data);
+                kfree(oldwork);
+        }
+        if (newwork) {
+                put_cred(newwork->data);
+                kfree(newwork);
+        }
         return ret;
 
+error_newwork:
+        kfree(newwork);
 error_keyring:
         key_ref_put(keyring_r);
         return ret;
-
-#else /* !TIF_NOTIFY_RESUME */
-        /*
-         * To be removed when TIF_NOTIFY_RESUME has been implemented on
-         * m68k/xtensa
-         */
-#warning TIF_NOTIFY_RESUME not implemented
-        return -EOPNOTSUPP;
-#endif /* !TIF_NOTIFY_RESUME */
 }
 
 /*
diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
index d71056db7b67..4ad54eea1ea4 100644
--- a/security/keys/process_keys.c
+++ b/security/keys/process_keys.c
@@ -834,23 +834,17 @@ 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_replace_session_keyring(void)
+void key_change_session_keyring(struct task_work *twork)
 {
-        const struct cred *old;
-        struct cred *new;
-
-        if (!current->replacement_session_keyring)
-                return;
+        const struct cred *old = current_cred();
+        struct cred *new = twork->data;
 
-        write_lock_irq(&tasklist_lock);
-        new = current->replacement_session_keyring;
-        current->replacement_session_keyring = NULL;
-        write_unlock_irq(&tasklist_lock);
-
-        if (!new)
+        kfree(twork);
+        if (unlikely(current->flags & PF_EXITING)) {
+                put_cred(new);
                 return;
+        }
 
-        old = current_cred();
         new->  uid      = old->  uid;
         new-> euid      = old-> euid;
         new-> suid      = old-> suid;