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Wed, 02 Sep 2026 03:58:20 -0700 (PDT) From: "Jonghyuk Kim(MalHyuk)" To: tursulin@ursulin.net, phasta@kernel.org, matthew.brost@intel.com, dakr@kernel.org Cc: christian.koenig@amd.com, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 2/2] drm/sched/tests: add a UAF regression test for the timeline name Date: Wed, 2 Sep 2026 19:58:08 +0900 Message-ID: <20260902105808.1541063-3-malhyuk97@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260902105808.1541063-1-malhyuk97@gmail.com> References: <20260902105808.1541063-1-malhyuk97@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 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) --- 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 +#include + +#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