From: Dan Carpenter <dan.carpenter@oracle.com>
Date: Tue, 8 May 2018 12:27:39 +0300
Subject: drm/xen-front: fix xen_drm_front_shbuf_alloc() error handling
Git-commit: 18f20bc5303cf6276cce9ae1742f3835244ad087
Patch-mainline: v4.18-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

The xen_drm_front_shbuf_alloc() function was returning a mix of error
pointers and NULL and the the caller wasn't checking correctly.  I've
changed it to always return error pointer consistently.

Fixes: c575b7eeb89f ("drm/xen-front: Add support for Xen PV display frontend")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Signed-off-by: Oleksandr Andrushchenko <oleksandr_andrushchenko@epam.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180508092739.GB661@mwanda

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/xen/xen_drm_front.c       |    4 ++--
 drivers/gpu/drm/xen/xen_drm_front_shbuf.c |    2 +-
 2 files changed, 3 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/xen/xen_drm_front.c
+++ b/drivers/gpu/drm/xen/xen_drm_front.c
@@ -188,8 +188,8 @@ int xen_drm_front_dbuf_create(struct xen
 	buf_cfg.be_alloc = front_info->cfg.be_alloc;
 
 	shbuf = xen_drm_front_shbuf_alloc(&buf_cfg);
-	if (!shbuf)
-		return -ENOMEM;
+	if (IS_ERR(shbuf))
+		return PTR_ERR(shbuf);
 
 	ret = dbuf_add_to_list(front_info, shbuf, dbuf_cookie);
 	if (ret < 0) {
--- a/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
+++ b/drivers/gpu/drm/xen/xen_drm_front_shbuf.c
@@ -383,7 +383,7 @@ xen_drm_front_shbuf_alloc(struct xen_drm
 
 	buf = kzalloc(sizeof(*buf), GFP_KERNEL);
 	if (!buf)
-		return NULL;
+		return ERR_PTR(-ENOMEM);
 
 	if (cfg->be_alloc)
 		buf->ops = &backend_ops;