On Thu, Sep 07, 2023 at 03:53:38PM +0200, Thomas Hellström wrote:
> when using __drm_kunit_helper_alloc_drm_device() the driver may be
> dereferenced by device-managed resources up until the device is
> freed, which is typically later than the kunit-managed resource code
> frees it. Fix this by simply make the driver device-managed as well.
>
> In short, the sequence leading to the UAF is as follows:
>
> INIT:
> Code allocates a struct device as a kunit-managed resource.
> Code allocates a drm driver as a kunit-managed resource.
> Code allocates a drm device as a device-managed resource.
>
> EXIT:
> Kunit resource cleanup frees the drm driver
> Kunit resource cleanup puts the struct device, which starts a
> device-managed resource cleanup
> device-managed cleanup calls drm_dev_put()
> drm_dev_put() dereferences the (now freed) drm driver -> Boom.
>
> Related KASAN message:
> [55272.551542] ==================================================================
> [55272.551551] BUG: KASAN: slab-use-after-free in drm_dev_put.part.0+0xd4/0xe0 [drm]
> [55272.551603] Read of size 8 at addr ffff888127502828 by task kunit_try_catch/10353
>
> [55272.551612] CPU: 4 PID: 10353 Comm: kunit_try_catch Tainted: G U N 6.5.0-rc7+ #155
> [55272.551620] Hardware name: ASUS System Product Name/PRIME B560M-A AC, BIOS 0403 01/26/2021
> [55272.551626] Call Trace:
> [55272.551629] <TASK>
> [55272.551633] dump_stack_lvl+0x57/0x90
> [55272.551639] print_report+0xcf/0x630
> [55272.551645] ? _raw_spin_lock_irqsave+0x5f/0x70
> [55272.551652] ? drm_dev_put.part.0+0xd4/0xe0 [drm]
> [55272.551694] kasan_report+0xd7/0x110
> [55272.551699] ? drm_dev_put.part.0+0xd4/0xe0 [drm]
> [55272.551742] drm_dev_put.part.0+0xd4/0xe0 [drm]
> [55272.551783] devres_release_all+0x15d/0x1f0
> [55272.551790] ? __pfx_devres_release_all+0x10/0x10
> [55272.551797] device_unbind_cleanup+0x16/0x1a0
> [55272.551802] device_release_driver_internal+0x3e5/0x540
> [55272.551808] ? kobject_put+0x5d/0x4b0
> [55272.551814] bus_remove_device+0x1f1/0x3f0
> [55272.551819] device_del+0x342/0x910
> [55272.551826] ? __pfx_device_del+0x10/0x10
> [55272.551830] ? lock_release+0x339/0x5e0
> [55272.551836] ? kunit_remove_resource+0x128/0x290 [kunit]
> [55272.551845] ? __pfx_lock_release+0x10/0x10
> [55272.551851] platform_device_del.part.0+0x1f/0x1e0
> [55272.551856] ? _raw_spin_unlock_irqrestore+0x30/0x60
> [55272.551863] kunit_remove_resource+0x195/0x290 [kunit]
> [55272.551871] ? _raw_spin_unlock_irqrestore+0x30/0x60
> [55272.551877] kunit_cleanup+0x78/0x120 [kunit]
> [55272.551885] ? __kthread_parkme+0xc1/0x1f0
> [55272.551891] ? __pfx_kunit_try_run_case_cleanup+0x10/0x10 [kunit]
> [55272.551900] ? __pfx_kunit_generic_run_threadfn_adapter+0x10/0x10 [kunit]
> [55272.551909] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit]
> [55272.551919] kthread+0x2e7/0x3c0
> [55272.551924] ? __pfx_kthread+0x10/0x10
> [55272.551929] ret_from_fork+0x2d/0x70
> [55272.551935] ? __pfx_kthread+0x10/0x10
> [55272.551940] ret_from_fork_asm+0x1b/0x30
> [55272.551948] </TASK>
>
> [55272.551953] Allocated by task 10351:
> [55272.551956] kasan_save_stack+0x1c/0x40
> [55272.551962] kasan_set_track+0x21/0x30
> [55272.551966] __kasan_kmalloc+0x8b/0x90
> [55272.551970] __kmalloc+0x5e/0x160
> [55272.551976] kunit_kmalloc_array+0x1c/0x50 [kunit]
> [55272.551984] drm_exec_test_init+0xfa/0x2c0 [drm_exec_test]
> [55272.551991] kunit_try_run_case+0xdd/0x250 [kunit]
> [55272.551999] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit]
> [55272.552008] kthread+0x2e7/0x3c0
> [55272.552012] ret_from_fork+0x2d/0x70
> [55272.552017] ret_from_fork_asm+0x1b/0x30
>
> [55272.552024] Freed by task 10353:
> [55272.552027] kasan_save_stack+0x1c/0x40
> [55272.552032] kasan_set_track+0x21/0x30
> [55272.552036] kasan_save_free_info+0x27/0x40
> [55272.552041] __kasan_slab_free+0x106/0x180
> [55272.552046] slab_free_freelist_hook+0xb3/0x160
> [55272.552051] __kmem_cache_free+0xb2/0x290
> [55272.552056] kunit_remove_resource+0x195/0x290 [kunit]
> [55272.552064] kunit_cleanup+0x78/0x120 [kunit]
> [55272.552072] kunit_generic_run_threadfn_adapter+0x4a/0x90 [kunit]
> [55272.552080] kthread+0x2e7/0x3c0
> [55272.552085] ret_from_fork+0x2d/0x70
> [55272.552089] ret_from_fork_asm+0x1b/0x30
>
> [55272.552096] The buggy address belongs to the object at ffff888127502800
> which belongs to the cache kmalloc-512 of size 512
> [55272.552105] The buggy address is located 40 bytes inside of
> freed 512-byte region [ffff888127502800, ffff888127502a00)
>
> [55272.552115] The buggy address belongs to the physical page:
> [55272.552119] page:00000000af6c70ff refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x127500
> [55272.552127] head:00000000af6c70ff order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
> [55272.552133] anon flags: 0x17ffffc0010200(slab|head|node=0|zone=2|lastcpupid=0x1fffff)
> [55272.552141] page_type: 0xffffffff()
> [55272.552145] raw: 0017ffffc0010200 ffff888100042c80 0000000000000000 dead000000000001
> [55272.552152] raw: 0000000000000000 0000000080200020 00000001ffffffff 0000000000000000
> [55272.552157] page dumped because: kasan: bad access detected
>
> [55272.552163] Memory state around the buggy address:
> [55272.552167] ffff888127502700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [55272.552173] ffff888127502780: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> [55272.552178] >ffff888127502800: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [55272.552184] ^
> [55272.552187] ffff888127502880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [55272.552193] ffff888127502900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> [55272.552198] ==================================================================
> [55272.552203] Disabling lock debugging due to kernel taint
>
> v2:
> - Update commit message, add Fixes: tag and Cc stable.
> v3:
> - Further commit message updates (Maxime Ripard).
>
> Cc: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
> Cc: Maxime Ripard <mripard@xxxxxxxxxx>
> Cc: Thomas Zimmermann <tzimmermann@xxxxxxx>
> Cc: David Airlie <airlied@xxxxxxxxx>
> Cc: Daniel Vetter <daniel@xxxxxxxx>
> Cc: dri-devel@xxxxxxxxxxxxxxxxxxxxx
> Cc: <stable@xxxxxxxxxxxxxxx> # v6.3+
> Fixes: d98780310719 ("drm/tests: helpers: Allow to pass a custom drm_driver")
> Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Reviewed-by: Francois Dugast <francois.dugast@xxxxxxxxx>
> ---
> include/drm/drm_kunit_helpers.h | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/include/drm/drm_kunit_helpers.h b/include/drm/drm_kunit_helpers.h
> index 514c8a7a32f0..ba483c87f0e7 100644
> --- a/include/drm/drm_kunit_helpers.h
> +++ b/include/drm/drm_kunit_helpers.h
> @@ -3,6 +3,8 @@
> #ifndef DRM_KUNIT_HELPERS_H_
> #define DRM_KUNIT_HELPERS_H_
>
> +#include <linux/device.h>
> +
> #include <kunit/test.h>
>
> struct drm_device;
> @@ -51,7 +53,7 @@ __drm_kunit_helper_alloc_drm_device(struct kunit *test,
> {
> struct drm_driver *driver;
>
> - driver = kunit_kzalloc(test, sizeof(*driver), GFP_KERNEL);
> + driver = devm_kzalloc(dev, sizeof(*driver), GFP_KERNEL);
> KUNIT_ASSERT_NOT_NULL(test, driver);
>
> driver->driver_features = features;
> --
> 2.41.0
>
