CVE-2023-53235 in Linux
Summary
by MITRE • 09/15/2025
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---
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Analysis
by VulDB Data Team • 01/11/2026
The vulnerability identified as CVE-2023-53235 resides within the Linux kernel's graphics subsystem, specifically in the direct rendering manager (drm) framework. This issue manifests as a use-after-free (UAF) condition that occurs during the execution of kernel unit tests, particularly when using the kunit testing framework. The flaw arises from an improper resource management sequence involving device-managed resources and kunit-managed resources, creating a temporal window where a drm driver structure is freed before all references to it are resolved. The vulnerability is categorized under CWE-416, which represents the use of freed memory, a common class of bugs in kernel development where objects are accessed after being deallocated. The UAF condition is triggered by the interaction between kunit's resource cleanup mechanism and the device manager's resource handling, leading to a scenario where device-managed resources attempt to dereference a drm driver that has already been freed by kunit's cleanup process.
The technical flaw involves a specific sequence of operations that leads to the UAF condition. Initially, the test code allocates a struct device as a kunit-managed resource, followed by a drm driver as another kunit-managed resource, and finally a drm device as a device-managed resource. During cleanup, kunit first frees the drm driver, then proceeds to free the struct device, which triggers device-managed resource cleanup. This cleanup process calls drm_dev_put(), which attempts to dereference the drm driver that was already freed by kunit, resulting in the use-after-free error. The KASAN (Kernel Address Sanitizer) report clearly traces this execution path, showing that drm_dev_put() is called from within devres_release_all(), which is invoked during device unbinding cleanup. This sequence is directly related to ATT&CK technique T1547.001, which involves the use of kernel modules and drivers to gain system-level access, as exploitation of such vulnerabilities could allow an attacker to execute arbitrary code with kernel privileges. The vulnerability is particularly concerning in testing environments where kernel modules are actively loaded and tested, as it can lead to system instability and potential privilege escalation.
The operational impact of this vulnerability is primarily confined to kernel testing environments, where it causes test failures and system crashes during the cleanup phase of unit tests. However, the implications extend beyond mere test instability, as the underlying resource management flaw could potentially be exploited in production environments if similar patterns exist elsewhere in the kernel codebase. The vulnerability demonstrates a critical design flaw in how kunit-managed resources interact with device-managed resources in the drm subsystem, where the lifecycle management of different resource types is not properly coordinated. This misalignment could result in kernel panics, system hangs, or more severe issues if exploited in a malicious context, particularly in environments where kernel modules are frequently loaded and unloaded. The vulnerability affects systems running Linux kernel versions where the drm subsystem is active and where kunit testing is utilized, making it relevant to kernel developers, system maintainers, and security researchers working with graphics drivers and kernel testing frameworks.
The mitigation strategy for this vulnerability involves modifying the resource management approach within the drm test helpers to ensure consistent lifecycle management of all resources involved. The fix implemented in the kernel involves making the drm driver itself device-managed, thereby ensuring that its cleanup occurs in the proper sequence with other device-managed resources. This approach aligns with the principle of resource management consistency, where all resources that might be referenced together are managed with the same lifecycle semantics. The fix prevents the UAF by ensuring that the drm driver remains valid for as long as device-managed resources that may reference it, eliminating the temporal window where the driver could be freed prematurely. This solution follows best practices for kernel development and addresses the root cause rather than merely patching symptoms, making it a robust and maintainable fix. The mitigation also emphasizes the importance of careful resource management in kernel code, particularly in testing frameworks where complex resource interactions are common. This approach reduces the likelihood of similar issues in other parts of the kernel where similar resource management patterns may be present, thereby improving overall kernel stability and security.