linux-kernel - [PATCH 4.19 67/90] drm/fb-helper: generic: Dont take module ref for fbcon

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Message-Id: <20190708150525.748813850@linuxfoundation.org>
Date:   Mon,  8 Jul 2019 17:13:34 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        Noralf Trønnes <noralf@...nnes.org>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 4.19 67/90] drm/fb-helper: generic: Dont take module ref for fbcon

[ Upstream commit 6ab20a05f4c7ed45632e24d5397d6284e192567d ]

It's now safe to let fbcon unbind automatically on fbdev unregister.
The crash problem was fixed in commit 2122b40580dd
("fbdev: fbcon: Fix unregister crash when more than one framebuffer")

Signed-off-by: Noralf Trønnes <noralf@...nnes.org>
Reviewed-by: Daniel Vetter <daniel.vetter@...ll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20190210131039.52664-13-noralf@tronnes.org
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/gpu/drm/drm_fb_helper.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
index a0663f44e218..8b546fde139d 100644
--- a/drivers/gpu/drm/drm_fb_helper.c
+++ b/drivers/gpu/drm/drm_fb_helper.c
@@ -2957,7 +2957,8 @@ static int drm_fbdev_fb_open(struct fb_info *info, int user)
 {
 	struct drm_fb_helper *fb_helper = info->par;
 
-	if (!try_module_get(fb_helper->dev->driver->fops->owner))
+	/* No need to take a ref for fbcon because it unbinds on unregister */
+	if (user && !try_module_get(fb_helper->dev->driver->fops->owner))
 		return -ENODEV;
 
 	return 0;
@@ -2967,7 +2968,8 @@ static int drm_fbdev_fb_release(struct fb_info *info, int user)
 {
 	struct drm_fb_helper *fb_helper = info->par;
 
-	module_put(fb_helper->dev->driver->fops->owner);
+	if (user)
+		module_put(fb_helper->dev->driver->fops->owner);
 
 	return 0;
 }
-- 
2.20.1