drm/i915: Fix NULL pointer dereference in capture_engine

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
Reviewed-by: Andi Shyti <andi.shyti@linux.intel.com>
Cc: John Harrison <John.C.Harrison@Intel.com>
Cc: <stable@vger.kernel.org> # v6.3+
Signed-off-by: Eugene Kobyak <eugene.kobyak@intel.com>
Signed-off-by: Andi Shyti <andi.shyti@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/xmsgfynkhycw3cf56akp4he2ffg44vuratocsysaowbsnhutzi@augnqbm777at

diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 135ded17334e549a97404f76ba64e96c0bcbd651..fee80a2df245819d76ee7a5dc2a18fdcf77f3e8a 100644 (file)
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -1643,9 +1643,21 @@ 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)) {
+               /*
+                * We want to know also what is the guc_id of the context,
+                * but if we don't have the context reference, then skip
+                * printing it.
+                */
+               if (ce)
+                       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);
+               else
+                       drm_info(&engine->gt->i915->drm,
+                                "Got hung context on %s with active request %lld:%lld not yet started\n",
+                                engine->name, rq->fence.context, rq->fence.seqno);
+       }
 
        if (rq) {
                capture = intel_engine_coredump_add_request(ee, rq, ATOMIC_MAYFAIL);