FAILED: patch "[PATCH] drm/atomic: Fix memleak on ERESTARTSYS during non-blocking" failed to apply to 4.14-stable tree

[<gregkh@xxxxxxxxxxxxxxxxxxx>]

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@xxxxxxxxxxxxxxx>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From 54f809cfbd6b4a43959039f5d33596ed3297ce16 Mon Sep 17 00:00:00 2001
From: "Leo (Sunpeng) Li" <sunpeng.li@xxxxxxx>
Date: Wed, 17 Jan 2018 12:51:08 +0100
Subject: [PATCH] drm/atomic: Fix memleak on ERESTARTSYS during non-blocking
 commits

During a non-blocking commit, it is possible to return before the
commit_tail work is queued (-ERESTARTSYS, for example).

Since a reference on the crtc commit object is obtained for the pending
vblank event when preparing the commit, the above situation will leave
us with an extra reference.

Therefore, if the commit_tail worker has not consumed the event at the
end of a commit, release it's reference.

Changes since v1:
- Also check for state->event->base.completion being set, to
  handle the case where stall_checks() fails in setup_crtc_commit().
Changes since v2:
- Add a flag to drm_crtc_commit, to prevent dereferencing a freed event.
  i915 may unreference the state in a worker.

Fixes: 24835e442f28 ("drm: reference count event->completion")
Cc: <stable@xxxxxxxxxxxxxxx> # v4.11+
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@xxxxxxx>
Acked-by: Harry Wentland <harry.wentland@xxxxxxx> #v1
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
Link: https://patchwork.freedesktop.org/patch/msgid/20180117115108.29608-1-maarten.lankhorst@xxxxxxxxxxxxxxx
Reviewed-by: Sean Paul <seanpaul@xxxxxxxxxxxx>

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index b16f1d69a0bb..e8c249361d7e 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1778,6 +1778,8 @@ int drm_atomic_helper_setup_commit(struct drm_atomic_state *state,
 		new_crtc_state->event->base.completion = &commit->flip_done;
 		new_crtc_state->event->base.completion_release = release_crtc_commit;
 		drm_crtc_commit_get(commit);
+
+		commit->abort_completion = true;
 	}
 
 	for_each_oldnew_connector_in_state(state, conn, old_conn_state, new_conn_state, i) {
@@ -3327,8 +3329,21 @@ EXPORT_SYMBOL(drm_atomic_helper_crtc_duplicate_state);
 void __drm_atomic_helper_crtc_destroy_state(struct drm_crtc_state *state)
 {
 	if (state->commit) {
+		/*
+		 * In the event that a non-blocking commit returns
+		 * -ERESTARTSYS before the commit_tail work is queued, we will
+		 * have an extra reference to the commit object. Release it, if
+		 * the event has not been consumed by the worker.
+		 *
+		 * state->event may be freed, so we can't directly look at
+		 * state->event->base.completion.
+		 */
+		if (state->event && state->commit->abort_completion)
+			drm_crtc_commit_put(state->commit);
+
 		kfree(state->commit->event);
 		state->commit->event = NULL;
+
 		drm_crtc_commit_put(state->commit);
 	}
 
diff --git a/include/drm/drm_atomic.h b/include/drm/drm_atomic.h
index 5afd6e364fb6..c63b0b48e884 100644
--- a/include/drm/drm_atomic.h
+++ b/include/drm/drm_atomic.h
@@ -134,6 +134,15 @@ struct drm_crtc_commit {
 	 * &drm_pending_vblank_event pointer to clean up private events.
 	 */
 	struct drm_pending_vblank_event *event;
+
+	/**
+	 * @abort_completion:
+	 *
+	 * A flag that's set after drm_atomic_helper_setup_commit takes a second
+	 * reference for the completion of $drm_crtc_state.event. It's used by
+	 * the free code to remove the second reference if commit fails.
+	 */
+	bool abort_completion;
 };
 
 struct __drm_planes_state {