1 files changed, 39 insertions, 21 deletions

diff --git a/kernel/fork.c b/kernel/fork.c
index e2cd3e2a5ae8..26a7a6707fa7 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -668,6 +668,38 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
         return mm;
 }
 
+static void complete_vfork_done(struct task_struct *tsk)
+{
+        struct completion *vfork;
+
+        task_lock(tsk);
+        vfork = tsk->vfork_done;
+        if (likely(vfork)) {
+                tsk->vfork_done = NULL;
+                complete(vfork);
+        }
+        task_unlock(tsk);
+}
+
+static int wait_for_vfork_done(struct task_struct *child,
+                                struct completion *vfork)
+{
+        int killed;
+
+        freezer_do_not_count();
+        killed = wait_for_completion_killable(vfork);
+        freezer_count();
+
+        if (killed) {
+                task_lock(child);
+                child->vfork_done = NULL;
+                task_unlock(child);
+        }
+
+        put_task_struct(child);
+        return killed;
+}
+
 /* Please note the differences between mmput and mm_release.
  * mmput is called whenever we stop holding onto a mm_struct,
  * error success whatever.
@@ -683,8 +715,6 @@ struct mm_struct *mm_access(struct task_struct *task, unsigned int mode)
  */
 void mm_release(struct task_struct *tsk, struct mm_struct *mm)
 {
-        struct completion *vfork_done = tsk->vfork_done;
-
         /* Get rid of any futexes when releasing the mm */
 #ifdef CONFIG_FUTEX
         if (unlikely(tsk->robust_list)) {
@@ -704,17 +734,15 @@ void mm_release(struct task_struct *tsk, struct mm_struct *mm)
         /* Get rid of any cached register state */
         deactivate_mm(tsk, mm);
 
-        /* notify parent sleeping on vfork() */
-        if (vfork_done) {
-                tsk->vfork_done = NULL;
-                complete(vfork_done);
-        }
+        if (tsk->vfork_done)
+                complete_vfork_done(tsk);
 
         /*
          * If we're exiting normally, clear a user-space tid field if
          * requested.  We leave this alone when dying by signal, to leave
          * the value intact in a core dump, and to save the unnecessary
-         * trouble otherwise.  Userland only wants this done for a sys_exit.
+         * trouble, say, a killed vfork parent shouldn't touch this mm.
+         * Userland only wants this done for a sys_exit.
          */
         if (tsk->clear_child_tid) {
                 if (!(tsk->flags & PF_SIGNALED) &&
@@ -1018,7 +1046,6 @@ static void copy_flags(unsigned long clone_flags, struct task_struct *p)
 
         new_flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER);
         new_flags |= PF_FORKNOEXEC;
-        new_flags |= PF_STARTING;
         p->flags = new_flags;
 }
 
@@ -1548,16 +1575,9 @@ long do_fork(unsigned long clone_flags,
                 if (clone_flags & CLONE_VFORK) {
                         p->vfork_done = &vfork;
                         init_completion(&vfork);
+                        get_task_struct(p);
                 }
 
-                /*
-                 * We set PF_STARTING at creation in case tracing wants to
-                 * use this to distinguish a fully live task from one that
-                 * hasn't finished SIGSTOP raising yet.  Now we clear it
-                 * and set the child going.
-                 */
-                p->flags &= ~PF_STARTING;
-
                 wake_up_new_task(p);
 
                 /* forking complete and child started to run, tell ptracer */
@@ -1565,10 +1585,8 @@ long do_fork(unsigned long clone_flags,
                         ptrace_event(trace, nr);
 
                 if (clone_flags & CLONE_VFORK) {
-                        freezer_do_not_count();
-                        wait_for_completion(&vfork);
-                        freezer_count();
-                        ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
+                        if (!wait_for_vfork_done(p, &vfork))
+                                ptrace_event(PTRACE_EVENT_VFORK_DONE, nr);
                 }
         } else {
                 nr = PTR_ERR(p);