[PATCH] drm/i915/gem: Do not leak siblings[] on proto context error

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

After a successful BALANCE/PARALLEL_SUBMIT extension on context
creation, error during processing of next user extension leaks
the siblings[] array. Fix that.

Discovered using AI-assisted static analysis confirmed by
Intel Product Security.

Reported-by: Martin Hodo <martin.hodo@intel.com>
Fixes: d4433c7600f7 ("drm/i915/gem: Use the proto-context to handle create parameters (v5)")
Cc: Faith Ekstrand <faith.ekstrand@collabora.com>
Cc: Simona Vetter <simona.vetter@ffwll.ch>
Cc: Tvrtko Ursulin <tvrtko.ursulin@igalia.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: <stable@vger.kernel.org> # v5.15+
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
---
 drivers/gpu/drm/i915/gem/i915_gem_context.c | 22 +++++++++++++--------
 1 file changed, 14 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index aeafe1742d30..87fce2adfeef 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -769,8 +769,8 @@ static int set_proto_ctx_engines(struct drm_i915_file_private *fpriv,
 		struct intel_engine_cs *engine;
 
 		if (copy_from_user(&ci, &user->engines[n], sizeof(ci))) {
-			kfree(set.engines);
-			return -EFAULT;
+			err = -EFAULT;
+			goto err;
 		}
 
 		memset(&set.engines[n], 0, sizeof(set.engines[n]));
@@ -786,8 +786,8 @@ static int set_proto_ctx_engines(struct drm_i915_file_private *fpriv,
 			drm_dbg(&i915->drm,
 				"Invalid engine[%d]: { class:%d, instance:%d }\n",
 				n, ci.engine_class, ci.engine_instance);
-			kfree(set.engines);
-			return -ENOENT;
+			err = -ENOENT;
+			goto err;
 		}
 
 		set.engines[n].type = I915_GEM_ENGINE_TYPE_PHYSICAL;
@@ -800,15 +800,21 @@ static int set_proto_ctx_engines(struct drm_i915_file_private *fpriv,
 					   set_proto_ctx_engines_extensions,
 					   ARRAY_SIZE(set_proto_ctx_engines_extensions),
 					   &set);
-	if (err) {
-		kfree(set.engines);
-		return err;
-	}
+	if (err)
+		goto err_extensions;
 
 	pc->num_user_engines = set.num_engines;
 	pc->user_engines = set.engines;
 
 	return 0;
+
+err_extensions:
+	for (n = 0; n < set.num_engines; n++)
+		kfree(set.engines[n].siblings);
+err:
+	kfree(set.engines);
+
+	return err;
 }
 
 static int set_proto_ctx_sseu(struct drm_i915_file_private *fpriv,
-- 
2.54.0