[PATCH v2 2/2] drm/sched/tests: add a UAF regression test for the timeline name

[Jonghyuk Kim(MalHyuk)]

Add a KUnit test that reproduces the drm_sched_fence get_timeline_name()
use-after-free fixed by the previous patch. It holds a reference on a job's
finished drm_sched_fence (standing in for a userspace sync_file), frees the
mock scheduler, then queries the timeline name through the public
dma_fence_timeline_name() API - as a SYNC_IOC_FILE_INFO consumer would.
Before the fix this triggers a KASAN slab-use-after-free read of the freed
scheduler; after it the cached name is returned and the test passes.

The test needs no hardware - it exercises the drm_sched core through the
existing mock scheduler under KASAN. Put it in a new tests_integration.c so
tests_basic.c stays focused on core scheduler behaviour.

Signed-off-by: Jonghyuk Kim(MalHyuk) <malhyuk97@xxxxxxxxx>
---
 drivers/gpu/drm/scheduler/tests/Makefile      |  1 +
 .../drm/scheduler/tests/tests_integration.c   | 83 +++++++++++++++++++
 2 files changed, 84 insertions(+)
 create mode 100644 drivers/gpu/drm/scheduler/tests/tests_integration.c

diff --git a/drivers/gpu/drm/scheduler/tests/Makefile b/drivers/gpu/drm/scheduler/tests/Makefile
index 9ec185fbbc15..10abe07c06d2 100644
--- a/drivers/gpu/drm/scheduler/tests/Makefile
+++ b/drivers/gpu/drm/scheduler/tests/Makefile
@@ -3,6 +3,7 @@
 drm-sched-tests-y := \
         mock_scheduler.o \
         tests_basic.o \
+        tests_integration.o \
         tests_scheduler.o
 
 obj-$(CONFIG_DRM_SCHED_KUNIT_TEST) += drm-sched-tests.o
diff --git a/drivers/gpu/drm/scheduler/tests/tests_integration.c b/drivers/gpu/drm/scheduler/tests/tests_integration.c
new file mode 100644
index 000000000000..0572f1e3a80b
--- /dev/null
+++ b/drivers/gpu/drm/scheduler/tests/tests_integration.c
@@ -0,0 +1,83 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2026 Jonghyuk Kim(MalHyuk) */
+
+#include <linux/dma-fence.h>
+#include <linux/rcupdate.h>
+
+#include "sched_tests.h"
+
+/*
+ * Integration tests exercising the drm_sched interaction with the wider
+ * dma-fence infrastructure, e.g. fences exported to userspace outliving the
+ * objects they were created from.
+ */
+
+/*
+ * Reproduce the drm_sched_fence get_timeline_name() lifetime bug.
+ *
+ * drm_sched_fence_get_timeline_name() reads the scheduler name, and the
+ * drm_sched_fence ops keep .release set, so the fence is NOT ops-detached on
+ * signal (dma_fence_signal_timestamp_locked() only clears ->ops for fences
+ * without .release/.wait). A driver that frees a per-context drm_gpu_scheduler
+ * while userspace still holds the exported ->finished fence (via sync_file /
+ * drm_syncobj) leaves the scheduler dangling; querying the timeline name then
+ * touches freed slab memory. KASAN reports a slab-use-after-free read in
+ * drm_sched_fence_get_timeline_name(). Confirmed instances: amdxdna, nouveau,
+ * msm; same class as CVE-2025-38703 (xe) and CVE-2025-71302 (panthor).
+ */
+static void drm_sched_dma_fence_timeline_name_uaf(struct kunit *test)
+{
+	struct drm_mock_sched_entity *entity;
+	struct drm_mock_scheduler *sched;
+	struct drm_mock_sched_job *job;
+	struct dma_fence *finished;
+	const char *name;
+	bool done;
+
+	sched = drm_mock_sched_new(test, MAX_SCHEDULE_TIMEOUT);
+	entity = drm_mock_sched_entity_new(test, DRM_SCHED_PRIORITY_NORMAL,
+					   sched);
+	job = drm_mock_sched_job_new(test, entity);
+
+	/* Arm + submit; the s_fence is only created by drm_sched_job_arm(). */
+	drm_mock_sched_job_submit(job);
+
+	/* Independent reference on the finished fence, as a sync_file would. */
+	finished = dma_fence_get(&job->base.s_fence->finished);
+
+	done = drm_mock_sched_job_wait_scheduled(job, HZ);
+	KUNIT_ASSERT_TRUE(test, done);
+	drm_mock_sched_advance(sched, 1);
+	done = drm_mock_sched_job_wait_finished(job, HZ);
+	KUNIT_ASSERT_TRUE(test, done);
+
+	/* Free the per-context scheduler while the finished fence is held. */
+	drm_mock_sched_entity_free(entity);
+	drm_mock_sched_fini(sched);
+	kunit_kfree(test, sched);
+
+	/*
+	 * Query the timeline name through the public dma-fence API, as a
+	 * userspace SYNC_IOC_FILE_INFO consumer would. Before the fix this is a
+	 * use-after-free read of the freed scheduler; after it the cached name
+	 * is returned and the test passes.
+	 */
+	rcu_read_lock();
+	name = (const char *)dma_fence_timeline_name(finished);
+	rcu_read_unlock();
+	kunit_info(test, "get_timeline_name() on stale fence returned %p\n", name);
+
+	dma_fence_put(finished);
+}
+
+static struct kunit_case drm_sched_dma_fence_uaf_tests[] = {
+	KUNIT_CASE(drm_sched_dma_fence_timeline_name_uaf),
+	{}
+};
+
+static struct kunit_suite drm_sched_dma_fence_uaf = {
+	.name = "drm-sched-dma-fence-uaf",
+	.test_cases = drm_sched_dma_fence_uaf_tests,
+};
+
+kunit_test_suite(drm_sched_dma_fence_uaf);
-- 
2.43.0