Re: [PATCH] drm/tests: provide exit function

[Maxime Ripard]

Hi,

On Wed, Sep 13, 2023 at 11:32:23AM +0300, José Pekkarinen wrote:
> Running drm_exec_test by modprobing the module I
> observe the following output:
> 
> [  424.471936] KTAP version 1
> [  424.471942] 1..1
> [  424.472446]     KTAP version 1
> [  424.472450]     # Subtest: drm_exec
> [  424.472453]     # module: drm_exec_test
> [  424.472459]     1..7
> [  424.479082] ==================================================================
> [  424.479095] BUG: KASAN: slab-use-after-free in drm_dev_put.part.0+0x4b/0x90 [drm]
> [  424.479426] Read of size 8 at addr ffff888132d3e028 by task kunit_try_catch/1866
> [  424.479436]
> [  424.479442] CPU: 1 PID: 1866 Comm: kunit_try_catch Tainted: G                 N 6.6.0-rc1-dirty #2

That's suspicious

> [  424.479446] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
> [  424.479446] Call Trace:
> [  424.479446]  <TASK>
> [  424.479446]  dump_stack_lvl+0x43/0x60
> [  424.479446]  print_report+0xcf/0x660
> [  424.479446]  ? __virt_addr_valid+0xd9/0x160
> [  424.479446]  ? drm_dev_put.part.0+0x4b/0x90 [drm]
> [  424.479446]  kasan_report+0xda/0x110
> [  424.479446]  ? drm_dev_put.part.0+0x4b/0x90 [drm]
> [  424.479446]  drm_dev_put.part.0+0x4b/0x90 [drm]
> [  424.479446]  release_nodes+0x83/0x160
> [  424.479446]  devres_release_all+0xe6/0x130
> [  424.479446]  ? __pfx_devres_release_all+0x10/0x10
> [  424.479446]  ? mutex_unlock+0x80/0xd0
> [  424.479446]  ? __pfx_mutex_unlock+0x10/0x10
> [  424.479446]  device_unbind_cleanup+0x16/0xc0
> [  424.479446]  device_release_driver_internal+0x28b/0x2e0
> [  424.479446]  bus_remove_device+0x124/0x1d0
> [  424.479446]  device_del+0x23d/0x580
> [  424.479446]  ? __pfx_device_del+0x10/0x10
> [  424.479446]  ? kasan_set_track+0x21/0x30
> [  424.479446]  ? _raw_spin_lock_irqsave+0x98/0xf0
> [  424.479446]  platform_device_del.part.0+0x19/0xe0
> [  424.479446]  kunit_remove_resource+0xfa/0x140 [kunit]
> [  424.479446]  kunit_cleanup+0x47/0xa0 [kunit]
> [  424.479446]  ? __pfx_kunit_try_run_case_cleanup+0x10/0x10 [kunit]
> [  424.479446]  ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [kunit]
> [  424.479446]  kunit_generic_run_threadfn_adapter+0x29/0x50 [kunit]
> [  424.479446]  kthread+0x184/0x1c0
> [  424.479446]  ? __pfx_kthread+0x10/0x10
> [  424.479446]  ret_from_fork+0x30/0x50
> [  424.479446]  ? __pfx_kthread+0x10/0x10
> [  424.479446]  ret_from_fork_asm+0x1b/0x30
> [  424.479446]  </TASK>
> [  424.479446]
> [  424.479446] Allocated by task 1865:
> [  424.479446]  kasan_save_stack+0x2f/0x50
> [  424.479446]  kasan_set_track+0x21/0x30
> [  424.479446]  __kasan_kmalloc+0xa6/0xb0
> [  424.479446]  __kmalloc+0x5d/0x160
> [  424.479446]  kunit_kmalloc_array+0x1c/0x50 [kunit]
> [  424.479446]  drm_exec_test_init+0xef/0x260 [drm_exec_test]
> [  424.479446]  kunit_try_run_case+0x6e/0x100 [kunit]
> [  424.479446]  kunit_generic_run_threadfn_adapter+0x29/0x50 [kunit]
> [  424.479446]  kthread+0x184/0x1c0
> [  424.479446]  ret_from_fork+0x30/0x50
> [  424.479446]  ret_from_fork_asm+0x1b/0x30
> [  424.479446]
> [  424.479446] Freed by task 1866:
> [  424.479446]  kasan_save_stack+0x2f/0x50
> [  424.479446]  kasan_set_track+0x21/0x30
> [  424.479446]  kasan_save_free_info+0x27/0x40
> [  424.479446]  ____kasan_slab_free+0x166/0x1c0
> [  424.479446]  slab_free_freelist_hook+0x9f/0x1e0
> [  424.479446]  __kmem_cache_free+0x187/0x2d0
> [  424.479446]  kunit_remove_resource+0xfa/0x140 [kunit]
> [  424.479446]  kunit_cleanup+0x47/0xa0 [kunit]
> [  424.479446]  kunit_generic_run_threadfn_adapter+0x29/0x50 [kunit]
> [  424.479446]  kthread+0x184/0x1c0
> [  424.479446]  ret_from_fork+0x30/0x50
> [  424.479446]  ret_from_fork_asm+0x1b/0x30
> [  424.479446]
> [  424.479446] The buggy address belongs to the object at ffff888132d3e000
> [  424.479446]  which belongs to the cache kmalloc-256 of size 256
> [  424.479446] The buggy address is located 40 bytes inside of
> [  424.479446]  freed 256-byte region [ffff888132d3e000, ffff888132d3e100)
> [  424.479446]
> [  424.479446] The buggy address belongs to the physical page:
> [  424.479446] page:0000000092ff6551 refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff888132d3f600 pfn:0x132d3c
> [  424.479446] head:0000000092ff6551 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> [  424.479446] ksm flags: 0x17ffffc0000840(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
> [  424.479446] page_type: 0xffffffff()
> [  424.479446] raw: 0017ffffc0000840 ffff888100042b40 ffffea00042c8000 dead000000000003
> [  424.479446] raw: ffff888132d3f600 000000008020001f 00000001ffffffff 0000000000000000
> [  424.479446] page dumped because: kasan: bad access detected
> [  424.479446]
> [  424.479446] Memory state around the buggy address:
> [  424.479446]  ffff888132d3df00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [  424.479446]  ffff888132d3df80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [  424.479446] >ffff888132d3e000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  424.479446]                                   ^
> [  424.479446]  ffff888132d3e080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [  424.479446]  ffff888132d3e100: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [  424.479446] ==================================================================
> [  424.481686] Disabling lock debugging due to kernel taint
> [  424.484124]     not ok 1 sanitycheck
> [  424.492981]     ok 2 test_lock
> [  424.503610]     ok 3 test_lock_unlock
> [  424.515058]     ok 4 test_duplicates
> [  424.530453]     ok 5 test_prepare
> [  424.539099]     ok 6 test_prepare_array
> [  424.550730]     ok 7 test_multiple_loops
> [  424.550743] # drm_exec: pass:6 fail:1 skip:0 total:7
> [  424.550750] # Totals: pass:6 fail:1 skip:0 total:7
> [  424.550756] not ok 5 drm_exec
> 
> The ouptut suggest the init function is allocating a drm_device
> that is not being freed. This patch provides the function and
> add it to the kunit_suite to produce the following result of
> the test:
> 
> [ 3363.342560] KTAP version 1
> [ 3363.342571] 1..1
> [ 3363.343090]     KTAP version 1
> [ 3363.343095]     # Subtest: drm_exec
> [ 3363.343098]     # module: drm_exec_test
> [ 3363.343103]     1..7
> [ 3363.353659]     ok 1 sanitycheck
> [ 3363.364281]     ok 2 test_lock
> [ 3363.375616]     ok 3 test_lock_unlock
> [ 3363.388741]     ok 4 test_duplicates
> [ 3363.402544]     ok 5 test_prepare
> [ 3363.413163]     ok 6 test_prepare_array
> [ 3363.424614]     ok 7 test_multiple_loops
> [ 3363.424630] # drm_exec: pass:7 fail:0 skip:0 total:7
> [ 3363.424637] # Totals: pass:7 fail:0 skip:0 total:7
> [ 3363.424643] ok 1 drm_exec
> 
> Signed-off-by: José Pekkarinen <jose.pekkarinen@xxxxxxxxxxx>
> ---
>  drivers/gpu/drm/tests/drm_exec_test.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/drivers/gpu/drm/tests/drm_exec_test.c b/drivers/gpu/drm/tests/drm_exec_test.c
> index 563949d777dd..7ff6bc6467d4 100644
> --- a/drivers/gpu/drm/tests/drm_exec_test.c
> +++ b/drivers/gpu/drm/tests/drm_exec_test.c
> @@ -42,6 +42,19 @@ static int drm_exec_test_init(struct kunit *test)
>  	return 0;
>  }
>  
> +static void drm_exec_test_exit(struct kunit *test)
> +{
> +	struct drm_exec_priv *priv = test->priv;
> +
> +	drm_kunit_helper_free_device(test, priv->dev);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->dev);

This shouldn't be necessary at all since 4f2b0b583baa.

> +	drm_dev_put(priv->drm);
> +	KUNIT_ASSERT_NOT_ERR_OR_NULL(test, priv->drm);

This isn't needed with devm_drm_dev_alloc

> +	kunit_kfree(test, priv);

And that's not needed either, kunit actions will be run automatically.

Maxime

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