[PATCH v3] drm/i915: Fixed NULL pointer dereference in capture_engine

[Eugene Kobyak]

When the intel_context structure contains NULL,
it raises a NULL pointer dereference error in drm_info().

Fixes: e8a3319c31a1 ("drm/i915: Allow error capture without a request")
Closes: https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/12309

Signed-off-by: Eugene Kobyak <eugene.kobyak at intel.com>
---
 drivers/gpu/drm/i915/i915_gpu_error.c | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 135ded17334e..1c614c74c2cf 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1643,9 +1643,16 @@ capture_engine(struct intel_engine_cs *engine,
 		return NULL;
 
 	intel_engine_get_hung_entity(engine, &ce, &rq);
-	if (rq && !i915_request_started(rq))
-		drm_info(&engine->gt->i915->drm, "Got hung context on %s with active request %lld:%lld [0x%04X] not yet started\n",
-			 engine->name, rq->fence.context, rq->fence.seqno, ce->guc_id.id);
+	if (rq && !i915_request_started(rq)) {
+		char guc_id[9];
+		if (ce)
+			scnprintf(guc_id, sizeof(guc_id), "[0x%04X]", ce->guc_id.id);
+		else
+			scnprintf(guc_id, sizeof(guc_id), " ");
+
+		drm_info(&engine->gt->i915->drm, "Got hung context on %s with active request %lld:%lld%s not yet started\n",
+			 engine->name, rq->fence.context, rq->fence.seqno, guc_id);
+	}
 
 	if (rq) {
 		capture = intel_engine_coredump_add_request(ee, rq, ATOMIC_MAYFAIL);
-- 
2.34.1