[PATCH V2 RESEND] drm_crtc: check if fb_create return NULL

[Su, Xuemin]

From: xueminsu <xuemin.su at intel.com>
Date: Tue, 22 Jan 2013 22:39:39 +0800
Subject: [PATCH] drm_crtc: check if fb_create return NULL

Some buggy driver may still return NULL in fb_create,
which leads to kernel panic.

Signed-off-by: xueminsu <xuemin.su at intel.com>
---
 drivers/gpu/drm/drm_crtc.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index f2d667b..b748498 100644
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -2172,6 +2172,13 @@ int drm_mode_addfb(struct drm_device *dev,
 		ret = PTR_ERR(fb);
 		goto out;
 	}
+	/* some buggy driver may return NULL here, which may cause panic */
+	if (!fb) {
+		WARN(1, "%pf should not return NULL.",
+			dev->mode_config.funcs->fb_create);
+		ret = -EINVAL;
+		goto out;
+	}
 
 	or->fb_id = fb->base.id;
 	list_add(&fb->filp_head, &file_priv->fbs);
-- 
1.7.6