BackMerge tag 'v4.15-rc8' into drm-next

Linux 4.15-rc8

Daniel requested this for so the intel CI won't fall over on drm-next
so often.

1 files changed, 18 insertions, 2 deletions

diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
index ac9a4e65ca49..41a75f9f23fd 100644
--- a/fs/userfaultfd.c
+++ b/fs/userfaultfd.c
@@ -570,11 +570,14 @@ out:
 static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
 					      struct userfaultfd_wait_queue *ewq)
 {
+	struct userfaultfd_ctx *release_new_ctx;
+
 	if (WARN_ON_ONCE(current->flags & PF_EXITING))
 		goto out;
 
 	ewq->ctx = ctx;
 	init_waitqueue_entry(&ewq->wq, current);
+	release_new_ctx = NULL;
 
 	spin_lock(&ctx->event_wqh.lock);
 	/*
@@ -601,8 +604,7 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
 				new = (struct userfaultfd_ctx *)
 					(unsigned long)
 					ewq->msg.arg.reserved.reserved1;
-
-				userfaultfd_ctx_put(new);
+				release_new_ctx = new;
 			}
 			break;
 		}
@@ -617,6 +619,20 @@ static void userfaultfd_event_wait_completion(struct userfaultfd_ctx *ctx,
 	__set_current_state(TASK_RUNNING);
 	spin_unlock(&ctx->event_wqh.lock);
 
+	if (release_new_ctx) {
+		struct vm_area_struct *vma;
+		struct mm_struct *mm = release_new_ctx->mm;
+
+		/* the various vma->vm_userfaultfd_ctx still points to it */
+		down_write(&mm->mmap_sem);
+		for (vma = mm->mmap; vma; vma = vma->vm_next)
+			if (vma->vm_userfaultfd_ctx.ctx == release_new_ctx)
+				vma->vm_userfaultfd_ctx = NULL_VM_UFFD_CTX;
+		up_write(&mm->mmap_sem);
+
+		userfaultfd_ctx_put(release_new_ctx);
+	}
+
 	/*
 	 * ctx may go away after this if the userfault pseudo fd is
 	 * already released.