[PATCH][next] drm/i915: Fix dereference of pointer backup before it is null checked

[Colin King <colin.king@canonical.com>]

From: Colin Ian King <colin.king@canonical.com>

The assignment of pointer backup_bo dereferences pointer backup before
backup is null checked, this could lead to a null pointer dereference
issue. Fix this by only assigning backup_bo after backup has been null
checked.

Addresses-Coverity: ("Dereference before null check")
Fixes: c56ce9565374 ("drm/i915 Implement LMEM backup and restore for suspend / resume")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
index 3b6d14b5c604..4ec6c557083a 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm_pm.c
@@ -149,7 +149,7 @@ static int i915_ttm_restore(struct i915_gem_apply_to_region *apply,
 	struct i915_gem_ttm_pm_apply *pm_apply =
 		container_of(apply, typeof(*pm_apply), base);
 	struct drm_i915_gem_object *backup = obj->ttm.backup;
-	struct ttm_buffer_object *backup_bo = i915_gem_to_ttm(backup);
+	struct ttm_buffer_object *backup_bo;
 	struct ttm_operation_ctx ctx = {};
 	int err;
 
@@ -163,6 +163,8 @@ static int i915_ttm_restore(struct i915_gem_apply_to_region *apply,
 	if (err)
 		return err;
 
+	backup_bo = i915_gem_to_ttm(backup);
+
 	/* Content may have been swapped. */
 	err = ttm_tt_populate(backup_bo->bdev, backup_bo->ttm, &ctx);
 	if (!err) {
-- 
2.32.0