Patch "drm/atomic: Fix memleak on ERESTARTSYS during non-blocking commits" has been added to the 4.15-stable tree

[<gregkh@linuxfoundation.org>]

This is a note to let you know that I've just added the patch titled

    drm/atomic: Fix memleak on ERESTARTSYS during non-blocking commits

to the 4.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     drm-atomic-fix-memleak-on-erestartsys-during-non-blocking-commits.patch
and it can be found in the queue-4.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


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

From: Leo (Sunpeng) Li <sunpeng.li@amd.com>

commit 54f809cfbd6b4a43959039f5d33596ed3297ce16 upstream.

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@vger.kernel.org> # v4.11+
Signed-off-by: Leo (Sunpeng) Li <sunpeng.li@amd.com>
Acked-by: Harry Wentland <harry.wentland@amd.com> #v1
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180117115108.29608-1-maarten.lankhorst@linux.intel.com
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/gpu/drm/drm_atomic_helper.c |   15 +++++++++++++++
 include/drm/drm_atomic.h            |    9 +++++++++
 2 files changed, 24 insertions(+)

--- 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(struc
 		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_dup
 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);
 	}
 
--- 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 {


Patches currently in stable-queue which might be from sunpeng.li@amd.com are

queue-4.15/drm-atomic-fix-memleak-on-erestartsys-during-non-blocking-commits.patch