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

From: Maxime Ripard
Date: Thu Sep 14 2023 - 08:00:43 EST

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On Wed, Sep 13, 2023 at 07:35:57PM +0300, José Pekkarinen wrote:
> On 2023-09-13 17:41, mripard@xxxxxxxxxx wrote:
> > On Wed, Sep 13, 2023 at 05:01:40PM +0300, José Pekkarinen wrote:
> > > On 2023-09-13 12:50, Maxime Ripard wrote:
> > > > 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.
> > >
> > >
> > > Reading this suggested patch I see only references to
> > > platform_driver_unregister, platform_device_put, and
> > > platform_device_del, not the ones used in this patch.
> >
> > I mean, what is drm_kunit_helper_free_device calling?
>
> That seems to be triggering any registered release
> action immediately, so it calls platform_device_del,
> followed by platform_device_put, followed by
> platform_driver_unregister.

Please test with:
https://lore.kernel.org/all/20230907135339.7971-2-thomas.hellstrom@xxxxxxxxxxxxxxx/

Maxime

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