linux-kernel - [PATCH 4.19 34/45] drm: Reorder set_property_atomic to avoid returning with an active ww

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Message-Id: <20190326042704.463433831@linuxfoundation.org>
Date:   Tue, 26 Mar 2019 15:30:17 +0900
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+6ea337c427f5083ebdf2@...kaller.appspotmail.com,
        Chris Wilson <chris@...is-wilson.co.uk>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Sean Paul <sean@...rly.run>, David Airlie <airlied@...ux.ie>
Subject: [PATCH 4.19 34/45] drm: Reorder set_property_atomic to avoid returning with an active ww_ctx

4.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Chris Wilson <chris@...is-wilson.co.uk>

commit 227ad6d957898a88b1746e30234ece64d305f066 upstream.

Delay the drm_modeset_acquire_init() until after we check for an
allocation failure so that we can return immediately upon error without
having to unwind.

WARNING: lock held when returning to user space!
4.20.0+ #174 Not tainted
------------------------------------------------
syz-executor556/8153 is leaving the kernel with locks still held!
1 lock held by syz-executor556/8153:
  #0: 000000005100c85c (crtc_ww_class_acquire){+.+.}, at:
set_property_atomic+0xb3/0x330 drivers/gpu/drm/drm_mode_object.c:462

Reported-by: syzbot+6ea337c427f5083ebdf2@...kaller.appspotmail.com
Fixes: 144a7999d633 ("drm: Handle properties in the core for atomic drivers")
Signed-off-by: Chris Wilson <chris@...is-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Cc: Sean Paul <sean@...rly.run>
Cc: David Airlie <airlied@...ux.ie>
Cc: <stable@...r.kernel.org> # v4.14+
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181230122842.21917-1-chris@chris-wilson.co.uk
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/gpu/drm/drm_mode_object.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/drm_mode_object.c
+++ b/drivers/gpu/drm/drm_mode_object.c
@@ -458,12 +458,13 @@ static int set_property_atomic(struct dr
 	struct drm_modeset_acquire_ctx ctx;
 	int ret;
 
-	drm_modeset_acquire_init(&ctx, 0);
-
 	state = drm_atomic_state_alloc(dev);
 	if (!state)
 		return -ENOMEM;
+
+	drm_modeset_acquire_init(&ctx, 0);
 	state->acquire_ctx = &ctx;
+
 retry:
 	if (prop == state->dev->mode_config.dpms_property) {
 		if (obj->type != DRM_MODE_OBJECT_CONNECTOR) {