Hi Tvrtko,
On 2026-09-17 at 11:12:03 +0100, Tvrtko Ursulin wrote:
> A new test to roughly simulate the VK CTS suite where
> dEQP-VK.wsi.android.swapchain.render.* is hitting an use after free when a
> sync file is accessed after the xe submission queue has been destroyed.
>
> Abbreviated KASAN report:
>
> [IGT] xe_sync_file: starting subtest sync_file_race
> ==================================================================
> BUG: KASAN: slab-use-after-free in
> drm_sched_fence_get_timeline_name+0xa1/0xb0 [gpu_sched]
> Read of size 8 at addr ffff888126726020 by task xe_sync_file/2931
> ...
> Call Trace:
> <TASK>
> kasan_report+0xeb/0x130
> drm_sched_fence_get_timeline_name+0xa1/0xb0 [gpu_sched]
> sync_file_ioctl+0x3cb/0xb00
> ...
> Allocated by task 2931:
> __kmalloc_cache_noprof+0x1c2/0x410
> guc_exec_queue_init+0x1a8/0x1240 [xe]
> xe_exec_queue_create+0xe72/0x13b0 [xe]
> xe_exec_queue_create_ioctl+0x10d9/0x1770 [xe]
> drm_ioctl_kernel+0x179/0x300
> drm_ioctl+0x58f/0xcf0
> xe_drm_ioctl+0xe8/0x140 [xe]
> ...
> Freed by task 1689:
> kfree+0x106/0x3e0
> __guc_exec_queue_fini_async+0x144/0x2d0 [xe]
> process_one_work+0x610/0xdf0
> worker_thread+0x7c8/0x14b0
>
> Without KASAN this of course turns into a plain null pointer dereference.
>
> Signed-off-by: Tvrtko Ursulin <[email protected]>
> Cc: Lucas De Marchi <[email protected]>
> Cc: Matthew Brost <[email protected]>
> Cc: Rodrigo Vivi <[email protected]>
> Cc: Thomas Hellström <[email protected]>
> Cc: Christian König <[email protected]>
> Cc: [email protected]
> Reviewed-by: Rodrigo Vivi <[email protected]> # v2
LGTM
Acked-by: Kamil Konieczny <[email protected]>
Regards,
Kamil
> ---
> v2:
> - igt_main and igt_fixture tweaks. (Rodrigo)
>
> v3:
> - Add driver name checks.
>
> v4:
> - Restore alphabetical ordering in the makefile. (Kamil)
> ---
> tests/intel/xe_sync_file.c | 154 +++++++++++++++++++++++++++++++++++++
> tests/meson.build | 1 +
> 2 files changed, 155 insertions(+)
> create mode 100644 tests/intel/xe_sync_file.c
>
> diff --git a/tests/intel/xe_sync_file.c b/tests/intel/xe_sync_file.c
> new file mode 100644
> index 000000000000..842c3856a525
> --- /dev/null
> +++ b/tests/intel/xe_sync_file.c
> @@ -0,0 +1,154 @@
> +// SPDX-License-Identifier: MIT
> +/*
> + * Copyright © 2025 Google, Inc.
> + */
> +
> +/**
> + * TEST: Tests for sync file functionality
> + * Category: Core
> + * Mega feature: General Core features
> + * Sub-category: CMD submission
> + * Functionality: fences
> + */
> +
> +#include "igt.h"
> +#include "sync_file.h"
> +
> +#include "lib/igt_syncobj.h"
> +#include "lib/intel_reg.h"
> +
> +#include "xe_drm.h"
> +#include "xe/xe_ioctl.h"
> +#include "xe/xe_query.h"
> +
> +static int sync_file_get_status(int sync_file, char **driver_name)
> +{
> + struct sync_fence_info fence = { };
> + struct sync_file_info info = {
> + .num_fences = 1,
> + .sync_fence_info = to_user_pointer(&fence),
> + };
> +
> + do_ioctl(sync_file, SYNC_IOC_FILE_INFO, &info);
> + igt_assert_eq(info.num_fences, 1);
> +
> + igt_debug("'%s'/'%s' = %d\n",
> + fence.driver_name, fence.obj_name, fence.status);
> +
> + *driver_name = strdup(fence.driver_name);
> +
> + return fence.status;
> +}
> +
> +/**
> + * SUBTEST: sync_file_race
> + * Description: Check that we can safely query an exported sync file fd
> + * Test category: functionality test
> + */
> +static void test_race(int xe, struct drm_xe_engine_class_instance *eci)
> +{
> + uint32_t vm, bo, syncobj, bind_syncobj, *batch;
> + struct drm_xe_sync sync[2] = {
> + { .type = DRM_XE_SYNC_TYPE_SYNCOBJ,
> + .flags = DRM_XE_SYNC_FLAG_SIGNAL,
> + },
> + { .type = DRM_XE_SYNC_TYPE_SYNCOBJ,
> + .flags = DRM_XE_SYNC_FLAG_SIGNAL,
> + },
> + };
> + const uint32_t bbend = MI_BATCH_BUFFER_END;
> + struct drm_xe_exec exec = {
> + .address = 0x100000,
> + .num_batch_buffer = 1,
> + .num_syncs = 2,
> + .syncs = to_user_pointer(sync),
> + };
> + char *driver_name;
> + int sync_fence;
> + size_t size;
> +
> + vm = xe_vm_create(xe, 0, 0);
> +
> + size = xe_bb_size(xe, sizeof(bbend));
> + bo = xe_bo_create(xe, vm, size, vram_if_possible(xe, eci->gt_id),
> + DRM_XE_GEM_CREATE_FLAG_NEEDS_VISIBLE_VRAM);
> +
> + batch = xe_bo_map(xe, bo, size);
> + *batch = bbend;
> +
> + exec.exec_queue_id = xe_exec_queue_create(xe, vm, eci, 0);
> +
> + syncobj = syncobj_create(xe, 0);
> + bind_syncobj = syncobj_create(xe, 0);
> +
> + sync[0].handle = bind_syncobj;
> + xe_vm_bind_async(xe, vm, 0, bo, 0, exec.address, size, sync, 1);
> +
> + sync[0].flags &= ~DRM_XE_SYNC_FLAG_SIGNAL;
> + sync[0].handle = bind_syncobj;
> + sync[1].flags |= DRM_XE_SYNC_FLAG_SIGNAL;
> + sync[1].handle = syncobj;
> + xe_exec(xe, &exec);
> +
> + /* Export a sync file fence. */
> + sync_fence = syncobj_handle_to_fd(xe, sync[1].handle,
> +
> DRM_SYNCOBJ_HANDLE_TO_FD_FLAGS_EXPORT_SYNC_FILE);
> +
> + igt_assert(syncobj_wait(xe, &syncobj, 1, INT64_MAX, 0, NULL));
> + igt_assert(syncobj_wait(xe, &bind_syncobj, 1, INT64_MAX, 0, NULL));
> +
> + driver_name = NULL;
> + igt_assert_eq(sync_file_get_status(sync_fence, &driver_name), 1);
> + igt_assert(driver_name);
> + igt_assert(!strcmp(driver_name, "drm_sched"));
> + free(driver_name);
> +
> + sync[0].flags |= DRM_XE_SYNC_FLAG_SIGNAL;
> + syncobj_reset(xe, &sync[0].handle, 1);
> + xe_vm_unbind_async(xe, vm, 0, 0, exec.address, size, sync, 1);
> + igt_assert(syncobj_wait(xe, &sync[0].handle, 1, INT64_MAX, 0, NULL));
> +
> + syncobj_destroy(xe, syncobj);
> + xe_exec_queue_destroy(xe, exec.exec_queue_id);
> +
> + munmap(batch, size);
> + gem_close(xe, bo);
> +
> + syncobj_destroy(xe, bind_syncobj);
> + xe_vm_destroy(xe, vm);
> +
> + /* Give any delayed freeing time to run. */
> + sleep(1);
> +
> + /* This should still work and not crash the kernel. */
> + driver_name = NULL;
> + igt_assert_eq(sync_file_get_status(sync_fence, &driver_name), 1);
> +
> + /* And must not read the original timeline/driver name either! */
> + igt_assert(driver_name);
> + igt_assert(!strcmp(driver_name, "detached-driver"));
> + free(driver_name);
> +
> + close(sync_fence);
> +}
> +
> +int igt_main()
> +{
> + struct drm_xe_engine_class_instance *eci;
> + int xe;
> +
> + igt_fixture() {
> + xe = drm_open_driver(DRIVER_XE);
> + }
> +
> + igt_subtest("sync_file_race") {
> + xe_for_each_engine(xe, eci) {
> + test_race(xe, eci);
> + break;
> + }
> + }
> +
> + igt_fixture() {
> + drm_close_driver(xe);
> + }
> +}
> diff --git a/tests/meson.build b/tests/meson.build
> index 1ac89bab7e15..43236b19b3a9 100644
> --- a/tests/meson.build
> +++ b/tests/meson.build
> @@ -347,6 +347,7 @@ intel_xe_progs = [
> 'xe_survivability',
> 'xe_sriov_vram',
> 'xe_svm_usrptr_madvise',
> + 'xe_sync_file',
> 'xe_sysfs_defaults',
> 'xe_sysfs_preempt_timeout',
> 'xe_sysfs_scheduler',
> --
> 2.55.0
>
