CVE-2023-53235

In the Linux kernel, the following vulnerability has been resolved:

drm/tests: helpers: Avoid a driver uaf

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+0x7 ---truncated---

This issue is limited to the DRM KUnit testing helpers and does not affect production kernels. The use-after-free could only be triggered when running unit tests with CONFIG_KUNIT enabled. In normal deployments without KUnit, the bug is not reachable and poses no security risk.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.