Re: [PATCH] drm/amd/display: Fix use-after-free bugs in KUnit tests

On 7/29/26 15:24, John Harrison wrote:
> On 7/24/26 14:36, Alex Hung wrote:
>> On 7/24/26 15:09, John Harrison wrote:
>>> On 7/24/26 12:37, Alex Hung wrote:
>>>> Reviewed-by: Alex Hung <[email protected]>
>>>>
>>>> With two comments:
>>>> 1. There is a minor conflicts on include
>>>> 2. The following code seems to have the same patterns (passing to 
>>>> drmm_* functions). Do they need to be changed too?
>>> None of those functions exist in my tree. Which might also explain 
>>> the include conflict. I'm using drm-tip fetched the same day I posted 
>>> the patch. Should I be basing the patch on a different tree?
>>
>> My bad. My local branch contains additional patches.
>>
>> I will create a patch for this four additional changes. Thanks for 
>> pointing this out.
> Can this patch be merged? It would be good to get the existing issues 
> fixed.

Hi John,

This patch is merged in Alex Deucher's amd-staging-drm-nex tree 
(https://gitlab.freedesktop.org/agd5f/linux)

The commit is 
https://gitlab.freedesktop.org/agd5f/linux/-/commit/637871507797e15bb109cec428877e56cfd94266

> 
> Thanks,
> John.
> 
>>
>>>
>>> John.
>>>
>>>
>>>>
>>>>
>>>> --- drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>> amdgpu_dm_connector_test.c
>>>> +++ drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>> amdgpu_dm_connector_test.c
>>>> @@ -3645,7 +3645,7 @@ static struct dm_test_stream_ctx 
>>>> *dm_test_stream_ctx_alloc(struct kunit *test)
>>>> DRIVER_MODESET);
>>>>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->drm);
>>>>
>>>> -       ctx->aconnector = kunit_kzalloc(test, sizeof(*ctx- 
>>>> >aconnector), GFP_KERNEL);
>>>> +       ctx->aconnector = drmm_kzalloc(ctx->drm, sizeof(*ctx- 
>>>> >aconnector), GFP_KERNEL);
>>>>         KUNIT_ASSERT_NOT_NULL(test, ctx->aconnector);
>>>>         KUNIT_ASSERT_EQ(test,
>>>>                 drmm_connector_init(ctx->drm, &ctx->aconnector->base,
>>>> @@ -3903,7 +3903,7 @@ static void 
>>>> dm_test_poll_dac_load_returns_cached(struct kunit *test)
>>>>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>         adev = drm_to_adev(drm);
>>>>
>>>> -       aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>> GFP_KERNEL);
>>>> +       aconnector = drmm_kzalloc(drm, sizeof(*aconnector), 
>>>> GFP_KERNEL);
>>>>         KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>         KUNIT_ASSERT_EQ(test,
>>>>                 drmm_connector_init(drm, &aconnector->base,
>>>> @@ -3950,7 +3950,7 @@ static struct amdgpu_dm_connector 
>>>> *dm_test_reg_connector(struct kunit *test)
>>>> DRIVER_MODESET);
>>>>         KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>
>>>> -       aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>> GFP_KERNEL);
>>>> +       aconnector = drmm_kzalloc(drm, sizeof(*aconnector), 
>>>> GFP_KERNEL);
>>>>         KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>         KUNIT_ASSERT_EQ(test,
>>>>                 drmm_connector_init(drm, &aconnector->base,
>>>> @@ -4405,7 +4405,7 @@ dm_test_modes_ctx_alloc(struct kunit *test, 
>>>> int connector_type)
>>>>         ctx->drm = dm_test_alloc_drm(test);
>>>>         ctx->aconnector = dm_test_add_connector(test, ctx->drm, 
>>>> connector_type);
>>>>
>>>> -       ctx->aenc = kunit_kzalloc(test, sizeof(*ctx->aenc), 
>>>> GFP_KERNEL);
>>>> +       ctx->aenc = drmm_kzalloc(ctx->drm, sizeof(*ctx->aenc), 
>>>> GFP_KERNEL);
>>>>         KUNIT_ASSERT_NOT_NULL(test, ctx->aenc);
>>>>         KUNIT_ASSERT_EQ(test,
>>>>                         drmm_encoder_init(ctx->drm, &ctx->aenc- 
>>>> >base, NULL,
>>>>
>>>>
>>>> On 7/23/26 17:35, John Harrison wrote:
>>>>> When running the KUnit tests with memory debugging enabled, a bunch of
>>>>> use-after-free errors are hit. These are due to using KUnit managed
>>>>> memory for the test objects but then giving them over to DRM managed
>>>>> objects. The KUnit stuff is deallocated first and when the DRM side
>>>>> calls its clean up helpers, it hits memory that has been freed 
>>>>> already.
>>>>>
>>>>> NB: There is still a use-after-free bug in the writeback tests.
>>>>> However, fixing that requires driver side changes as well as test side
>>>>> changes. Those changes are part of:
>>>>>    https://patchwork.freedesktop.org/series/152420/
>>>>>
>>>>> Signed-off-by: John Harrison <[email protected]>
>>>>> CC: Alex Hung <[email protected]>
>>>>> CC: Harry Wentland <[email protected]>
>>>>> ---
>>>>>   .../tests/amdgpu_dm_connector_test.c          | 37 +++++++++ 
>>>>> +---------
>>>>>   .../amdgpu_dm/tests/amdgpu_dm_kunit_helpers.c |  3 +-
>>>>>   .../amdgpu_dm/tests/amdgpu_dm_wb_test.c       |  5 ++-
>>>>>   3 files changed, 24 insertions(+), 21 deletions(-)
>>>>>
>>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_connector_test.c b/drivers/gpu/drm/amd/display/amdgpu_dm/ 
>>>>> tests/amdgpu_dm_connector_test.c
>>>>> index 0a5d439f66c3..93a854d4fdfa 100644
>>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_connector_test.c
>>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_connector_test.c
>>>>> @@ -12,6 +12,7 @@
>>>>>   #include <drm/drm_crtc.h>
>>>>>   #include <drm/drm_edid.h>
>>>>>   #include <drm/drm_kunit_helpers.h>
>>>>> +#include <drm/drm_managed.h>
>>>>>   #include <drm/drm_mode_object.h>
>>>>>   #include <drm/drm_property.h>
>>>>>   #include <linux/hdmi.h>
>>>>> @@ -1449,7 +1450,7 @@ static void 
>>>>> dm_test_funcs_reset_sets_defaults(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    connector = kunit_kzalloc(test, sizeof(*connector), 
>>>>> GFP_KERNEL);
>>>>> +    connector = drmm_kzalloc(drm, sizeof(*connector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, connector);
>>>>>         drmm_connector_init(drm, connector, &dm_test_connector_funcs,
>>>>> @@ -1488,7 +1489,7 @@ static void 
>>>>> dm_test_funcs_reset_edp_abm_level(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    connector = kunit_kzalloc(test, sizeof(*connector), 
>>>>> GFP_KERNEL);
>>>>> +    connector = drmm_kzalloc(drm, sizeof(*connector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, connector);
>>>>>         drmm_connector_init(drm, connector, &dm_test_connector_funcs,
>>>>> @@ -1526,7 +1527,7 @@ static void 
>>>>> dm_test_funcs_reset_edp_abm_disabled(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    connector = kunit_kzalloc(test, sizeof(*connector), 
>>>>> GFP_KERNEL);
>>>>> +    connector = drmm_kzalloc(drm, sizeof(*connector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, connector);
>>>>>         drmm_connector_init(drm, connector, &dm_test_connector_funcs,
>>>>> @@ -1568,7 +1569,7 @@ static void 
>>>>> dm_test_atomic_dup_state_copies_fields(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    connector = kunit_kzalloc(test, sizeof(*connector), 
>>>>> GFP_KERNEL);
>>>>> +    connector = drmm_kzalloc(drm, sizeof(*connector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, connector);
>>>>>         drmm_connector_init(drm, connector, &dm_test_connector_funcs,
>>>>> @@ -2359,8 +2360,8 @@ static void setup_panel_type_fixture(struct 
>>>>> kunit *test,
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fixture->drm);
>>>>>       fixture->adev = drm_to_adev(fixture->drm);
>>>>>   -    fixture->aconnector = kunit_kzalloc(test, sizeof(*fixture- 
>>>>> >aconnector),
>>>>> -                        GFP_KERNEL);
>>>>> +    fixture->aconnector = drmm_kzalloc(fixture->drm, 
>>>>> sizeof(*fixture->aconnector),
>>>>> +                       GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fixture->aconnector);
>>>>>       fixture->link = kunit_kzalloc(test, sizeof(*fixture->link), 
>>>>> GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, fixture->link);
>>>>> @@ -2554,9 +2555,9 @@ static void 
>>>>> dm_test_update_subconnector_dp_with_sink(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>>> GFP_KERNEL);
>>>>> +    aconnector = drmm_kzalloc(drm, sizeof(*aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>> -    link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL);
>>>>> +    link = drmm_kzalloc(drm, sizeof(*link), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, link);
>>>>>         drmm_connector_init(drm, &aconnector->base, 
>>>>> &dm_test_connector_funcs,
>>>>> @@ -2598,9 +2599,9 @@ static void 
>>>>> dm_test_update_subconnector_dp_no_sink(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>>> GFP_KERNEL);
>>>>> +    aconnector = drmm_kzalloc(drm, sizeof(*aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>> -    link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL);
>>>>> +    link = drmm_kzalloc(drm, sizeof(*link), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, link);
>>>>>         drmm_connector_init(drm, &aconnector->base, 
>>>>> &dm_test_connector_funcs,
>>>>> @@ -2641,9 +2642,9 @@ static void 
>>>>> dm_test_update_subconnector_non_dp_noop(struct kunit *test)
>>>>>                              DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>>> GFP_KERNEL);
>>>>> +    aconnector = drmm_kzalloc(drm, sizeof(*aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>> -    link = kunit_kzalloc(test, sizeof(*link), GFP_KERNEL);
>>>>> +    link = drmm_kzalloc(drm, sizeof(*link), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, link);
>>>>>         drmm_connector_init(drm, &aconnector->base, 
>>>>> &dm_test_connector_funcs,
>>>>> @@ -2657,7 +2658,7 @@ static void 
>>>>> dm_test_update_subconnector_non_dp_noop(struct kunit *test)
>>>>>         link->dpcd_caps.dongle_type = 
>>>>> DISPLAY_DONGLE_DP_HDMI_CONVERTER;
>>>>>       aconnector->dc_link = link;
>>>>> -    aconnector->dc_sink = kunit_kzalloc(test, sizeof(*aconnector- 
>>>>> >dc_sink), GFP_KERNEL);
>>>>> +    aconnector->dc_sink = drmm_kzalloc(drm, sizeof(*aconnector- 
>>>>> >dc_sink), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, aconnector->dc_sink);
>>>>>         update_subconnector_property(aconnector);
>>>>> @@ -2804,7 +2805,7 @@ static struct amdgpu_dm_connector 
>>>>> *dm_test_add_connector(struct kunit *test,
>>>>>   {
>>>>>       struct amdgpu_dm_connector *aconnector;
>>>>>   -    aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>>> GFP_KERNEL);
>>>>> +    aconnector = drmm_kzalloc(drm, sizeof(*aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>>         KUNIT_ASSERT_EQ(test,
>>>>> @@ -3103,7 +3104,7 @@ static struct dm_test_panel_ctx 
>>>>> *dm_test_panel_ctx_alloc(struct kunit *test)
>>>>>       KUNIT_ASSERT_NOT_NULL(test, prop);
>>>>>       ctx->drm->mode_config.panel_type_property = prop;
>>>>>   -    ctx->aconnector = kunit_kzalloc(test, sizeof(*ctx- 
>>>>> >aconnector), GFP_KERNEL);
>>>>> +    ctx->aconnector = drmm_kzalloc(ctx->drm, sizeof(*ctx- 
>>>>> >aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, ctx->aconnector);
>>>>>       KUNIT_ASSERT_EQ(test,
>>>>>           drmm_connector_init(ctx->drm, &ctx->aconnector->base,
>>>>> @@ -3112,7 +3113,7 @@ static struct dm_test_panel_ctx 
>>>>> *dm_test_panel_ctx_alloc(struct kunit *test)
>>>>> drm_object_attach_property(&ctx->aconnector->base.base, prop,
>>>>>                      DRM_MODE_PANEL_TYPE_UNKNOWN);
>>>>>   -    ctx->link = kunit_kzalloc(test, sizeof(*ctx->link), 
>>>>> GFP_KERNEL);
>>>>> +    ctx->link = drmm_kzalloc(ctx->drm, sizeof(*ctx->link), 
>>>>> GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, ctx->link);
>>>>>       ctx->aconnector->dc_link = ctx->link;
>>>>>   @@ -3376,14 +3377,14 @@ static struct dm_test_fill_ctx 
>>>>> *dm_test_fill_ctx_alloc(struct kunit *test)
>>>>>                                  DRIVER_MODESET);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, ctx->drm);
>>>>>   -    ctx->aconnector = kunit_kzalloc(test, sizeof(*ctx- 
>>>>> >aconnector), GFP_KERNEL);
>>>>> +    ctx->aconnector = drmm_kzalloc(ctx->drm, sizeof(*ctx- 
>>>>> >aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, ctx->aconnector);
>>>>>       KUNIT_ASSERT_EQ(test,
>>>>>           drmm_connector_init(ctx->drm, &ctx->aconnector->base,
>>>>>                       &dm_test_connector_funcs,
>>>>>                       DRM_MODE_CONNECTOR_DisplayPort, NULL), 0);
>>>>>   -    ctx->conn_state = kunit_kzalloc(test, sizeof(*ctx- 
>>>>> >conn_state), GFP_KERNEL);
>>>>> +    ctx->conn_state = drmm_kzalloc(ctx->drm, sizeof(*ctx- 
>>>>> >conn_state), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, ctx->conn_state);
>>>>>       ctx->stream = kunit_kzalloc(test, sizeof(*ctx->stream), 
>>>>> GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, ctx->stream);
>>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_kunit_helpers.c b/drivers/gpu/drm/amd/display/amdgpu_dm/ 
>>>>> tests/amdgpu_dm_kunit_helpers.c
>>>>> index 58615cdbe854..7d5e3823b33b 100644
>>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_kunit_helpers.c
>>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_kunit_helpers.c
>>>>> @@ -8,6 +8,7 @@
>>>>>   #include <kunit/test.h>
>>>>>   #include <linux/module.h>
>>>>>   #include <drm/drm_kunit_helpers.h>
>>>>> +#include <drm/drm_managed.h>
>>>>>     #include "dc.h"
>>>>>   #include "core_types.h"
>>>>> @@ -127,7 +128,7 @@ struct amdgpu_dm_connector 
>>>>> *dm_kunit_alloc_connector(struct kunit *test,
>>>>>   {
>>>>>       struct amdgpu_dm_connector *aconnector;
>>>>>   -    aconnector = kunit_kzalloc(test, sizeof(*aconnector), 
>>>>> GFP_KERNEL);
>>>>> +    aconnector = drmm_kzalloc(adev_to_drm(adev), 
>>>>> sizeof(*aconnector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, aconnector);
>>>>>         if (adev)
>>>>> diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_wb_test.c b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/ 
>>>>> amdgpu_dm_wb_test.c
>>>>> index b43bc244487e..3454cf371414 100644
>>>>> --- a/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_wb_test.c
>>>>> +++ b/drivers/gpu/drm/amd/display/amdgpu_dm/tests/amdgpu_dm_wb_test.c
>>>>> @@ -12,6 +12,7 @@
>>>>>   #include <drm/drm_fourcc.h>
>>>>>   #include <drm/drm_framebuffer.h>
>>>>>   #include <drm/drm_kunit_helpers.h>
>>>>> +#include <drm/drm_managed.h>
>>>>>   #include <drm/drm_mode.h>
>>>>>   #include <drm/drm_modes.h>
>>>>>   #include <drm/drm_writeback.h>
>>>>> @@ -266,7 +267,7 @@ static void 
>>>>> dm_test_wb_get_modes_returns_modes(struct kunit *test)
>>>>>                              DRIVER_MODESET | DRIVER_ATOMIC);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    connector = kunit_kzalloc(test, sizeof(*connector), 
>>>>> GFP_KERNEL);
>>>>> +    connector = drmm_kzalloc(drm, sizeof(*connector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, connector);
>>>>>         drmm_connector_init(drm, connector, 
>>>>> &dm_wb_test_connector_funcs,
>>>>> @@ -301,7 +302,7 @@ static void 
>>>>> dm_test_wb_get_modes_bounded_by_max(struct kunit *test)
>>>>>                              DRIVER_MODESET | DRIVER_ATOMIC);
>>>>>       KUNIT_ASSERT_NOT_ERR_OR_NULL(test, drm);
>>>>>   -    connector = kunit_kzalloc(test, sizeof(*connector), 
>>>>> GFP_KERNEL);
>>>>> +    connector = drmm_kzalloc(drm, sizeof(*connector), GFP_KERNEL);
>>>>>       KUNIT_ASSERT_NOT_NULL(test, connector);
>>>>>         drmm_connector_init(drm, connector, 
>>>>> &dm_wb_test_connector_funcs,
>>>>
>>>
>>
>