CVE-2022-49827 in Linux
Summary
by MITRE • 05/01/2025
In the Linux kernel, the following vulnerability has been resolved:
drm: Fix potential null-ptr-deref in drm_vblank_destroy_worker()
drm_vblank_init() call drmm_add_action_or_reset() with drm_vblank_init_release() as action. If __drmm_add_action() failed, will directly call drm_vblank_init_release() with the vblank whose worker is NULL. As the resule, a null-ptr-deref will happen in kthread_destroy_worker(). Add the NULL check before calling drm_vblank_destroy_worker().
BUG: null-ptr-deref KASAN: null-ptr-deref in range [0x0000000000000068-0x000000000000006f]
CPU: 5 PID: 961 Comm: modprobe Not tainted 6.0.0-11331-gd465bff130bf-dirty RIP: 0010:kthread_destroy_worker+0x25/0xb0 Call Trace: <TASK> drm_vblank_init_release+0x124/0x220 [drm]
? drm_crtc_vblank_restore+0x8b0/0x8b0 [drm]
__drmm_add_action_or_reset+0x41/0x50 [drm]
drm_vblank_init+0x282/0x310 [drm]
vkms_init+0x35f/0x1000 [vkms]
? 0xffffffffc4508000 ? lock_is_held_type+0xd7/0x130 ? __kmem_cache_alloc_node+0x1c2/0x2b0 ? lock_is_held_type+0xd7/0x130 ? 0xffffffffc4508000 do_one_initcall+0xd0/0x4f0 ... do_syscall_64+0x35/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0
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Analysis
by VulDB Data Team • 11/10/2025
The vulnerability described in CVE-2022-49827 represents a critical null pointer dereference issue within the Linux kernel's direct rendering manager subsystem. This flaw specifically affects the drm_vblank_destroy_worker() function where improper error handling leads to execution of code with a null worker pointer, resulting in a kernel panic. The vulnerability manifests during the initialization process of vblank infrastructure when drm_vblank_init() attempts to register cleanup actions through drmm_add_action_or_reset() with drm_vblank_init_release() as the callback function. When the underlying __drmm_add_action() operation fails, the system proceeds to invoke drm_vblank_init_release() with a vblank structure whose worker field remains uninitialized and set to NULL. This condition directly triggers a null pointer dereference in kthread_destroy_worker() function, which is part of the kernel's thread management subsystem and operates under the kernel address sanitizer (KASAN) detection framework.
The technical implementation of this vulnerability stems from inadequate defensive programming practices within the DRM subsystem's resource management logic. The flaw occurs because the drm_vblank_init() function does not properly validate whether the worker pointer has been successfully initialized before proceeding with cleanup operations. This type of error falls under the CWE-476 category of Null Pointer Dereference, which is a fundamental security weakness that can lead to system instability and potential privilege escalation. The attack vector involves module loading operations, specifically when the vkms driver attempts to initialize vblank functionality, making this vulnerability particularly concerning for graphics-intensive applications and kernel module management systems. The vulnerability is classified as a kernel-level memory safety issue that can be exploited to cause denial of service conditions or potentially enable more sophisticated attacks if combined with other kernel vulnerabilities.
The operational impact of CVE-2022-49827 extends beyond simple system crashes, as it represents a fundamental breakdown in kernel resource management that can affect graphics subsystem stability across multiple device drivers. When this vulnerability is triggered, it results in immediate system instability and can cause complete system hangs or reboots, particularly in environments where graphics virtualization or display management is critical. The vulnerability affects any system running a Linux kernel version that includes the affected drm subsystem code, making it relevant to a broad range of embedded systems, desktop environments, and server configurations that utilize the direct rendering manager for graphics processing. The specific KASAN detection range [0x0000000000000068-0x000000000000006f] indicates that the null pointer dereference occurs at a very specific memory offset within the vblank structure, suggesting that the vulnerability is tightly coupled to the internal data structure layout and initialization sequence. This type of vulnerability would typically be classified under the ATT&CK technique T1068 for local privilege escalation or T1499 for system disruption, depending on the exploitation context and the specific system configuration.
The recommended mitigation for CVE-2022-49827 involves implementing proper null pointer validation before calling drm_vblank_destroy_worker() function, ensuring that the worker field is verified as non-null before proceeding with cleanup operations. This fix aligns with standard kernel development practices and security hardening guidelines that require defensive programming measures to prevent null pointer dereferences. The solution requires modification to the drm_vblank_init_release() function to include explicit null pointer checks before invoking kthread_destroy_worker(), which can be achieved through straightforward code modifications that add conditional logic to validate worker state. System administrators should prioritize applying kernel updates that contain the patched drm subsystem code, as this vulnerability cannot be effectively mitigated through configuration changes or runtime parameters. The fix should be applied across all systems running affected kernel versions, particularly in production environments where graphics processing stability is critical, and should be validated through comprehensive testing to ensure that the patched code does not introduce regressions in normal operation. Organizations should also implement monitoring systems to detect potential exploitation attempts or system instability related to graphics driver initialization processes.