[PATCH] drm/i915/guc: Fix potential null pointer deref in GuC 'steal id' test

[John.C.Harrison at Intel.com]

From: John Harrison <John.C.Harrison at Intel.com>

It was noticed that if the very first 'stealing' request failed to
create for some reason then the 'steal all ids' loop would immediately
exit with 'last' still being NULL. The test would attempt to continue
but using a null pointer. Fix that by aborting the test if it fails to
create any requests at all.

Signed-off-by: John Harrison <John.C.Harrison at Intel.com>
---
 drivers/gpu/drm/i915/gt/uc/selftest_guc.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gt/uc/selftest_guc.c b/drivers/gpu/drm/i915/gt/uc/selftest_guc.c
index 1fd760539f77b..bfb72143566f6 100644
--- a/drivers/gpu/drm/i915/gt/uc/selftest_guc.c
+++ b/drivers/gpu/drm/i915/gt/uc/selftest_guc.c
@@ -204,9 +204,9 @@ static int intel_guc_steal_guc_ids(void *arg)
 		if (IS_ERR(rq)) {
 			ret = PTR_ERR(rq);
 			rq = NULL;
-			if (ret != -EAGAIN) {
-				guc_err(guc, "Failed to create request %d: %pe\n",
-					context_index, ERR_PTR(ret));
+			if ((ret != -EAGAIN) || !last) {
+				guc_err(guc, "Failed to create %srequest %d: %pe\n",
+					last ? "" : "first ", context_index, ERR_PTR(ret));
 				goto err_spin_rq;
 			}
 		} else {
-- 
2.39.1