From e4d5dc218c4a1d1f555448825f5a8d7b1ac82959 Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris@chris-wilson.co.uk>
Date: Wed, 5 Jul 2017 15:26:31 +0100
Subject: [PATCH] drm/i915: Check new context against kernel_context after reporting an error
Git-commit: e4d5dc218c4a1d1f555448825f5a8d7b1ac82959
Patch-mainline: v4.14-rc1
References: FATE#322643 bsc#1055900

Avoid any pointer dereference in inspecting a potential PTR_ERR by
checking for the error pointer before checking for an invalid context.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20170705142634.18554-1-chris@chris-wilson.co.uk
Acked-by: Takashi Iwai <tiwai@suse.de>

---
 drivers/gpu/drm/i915/i915_gem_context.c |    5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -571,14 +571,13 @@ int i915_gem_context_open(struct drm_i91
 	mutex_lock(&i915->drm.struct_mutex);
 	ctx = i915_gem_create_context(i915, file_priv);
 	mutex_unlock(&i915->drm.struct_mutex);
-
-	GEM_BUG_ON(i915_gem_context_is_kernel(ctx));
-
 	if (IS_ERR(ctx)) {
 		idr_destroy(&file_priv->context_idr);
 		return PTR_ERR(ctx);
 	}
 
+	GEM_BUG_ON(i915_gem_context_is_kernel(ctx));
+
 	return 0;
 }