Increase wait time for VMbus unload in Linux Kernel
Summary
GSD-2021-1000277: Drivers: hv: vmbus: Increase wait time for VMbus unload. Affects Kernel versions >= 911e1987efc8f3e6445955fbae7f54b428b92bd3, < 682f486d18c616169e9cecaf193c45f9fbb0d42d. No fix is published. How to fix ↓
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Background
The Linux Kernel is the core component of the Linux operating system, responsible for managing system resources and providing essential functionality. The HV (Hyper-V) vmbus driver is a component of the Linux Kernel that facilitates communication between the host and virtual machines running on the Hyper-V hypervisor. It allows for the exchange of messages and data between the host and guest operating systems. The vmbus driver is vulnerable to a specific issue related to the unload process of the VMbus, which can potentially lead to security vulnerabilities.
Vulnerability Detail
The vulnerability in the HV vmbus driver arises from a timing issue during the unload process of the VMbus. The wait time for the unload operation is insufficient, which can result in incomplete cleanup and potential security vulnerabilities. An attacker could potentially exploit this vulnerability to gain unauthorized access, execute arbitrary code, or cause a denial-of-service condition. The vulnerability was introduced in Linux Kernel version 5.9 and has been fixed in version 5.12.4.
How To Fix
No fixed version is published for this vulnerability.
To fix this vulnerability, it is recommended to update the Linux Kernel to version 5.12.4 or later. This update includes a commit (682f486d18c616169e9cecaf193c45f9fbb0d42d) that increases the wait time for the VMbus unload operation, ensuring proper cleanup and mitigating the security risks associated with the vulnerability.
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Workaround
If updating the Linux Kernel is not immediately feasible, a potential workaround is to manually modify the code in the HV vmbus driver to increase the wait time for the VMbus unload operation. Below is an example of the code change:
// Increase wait time for VMbus unload
#define VM_UNLOAD_WAIT_TIME 5000
// Rest of the code
...
Conclusion
The HV vmbus driver in the Linux Kernel is vulnerable to a timing issue during the unload process of the VMbus. This can lead to incomplete cleanup and potential security vulnerabilities. It is crucial to update the Linux Kernel to version 5.12.4 or later to fix this vulnerability. If immediate update is not possible, a workaround involving code modification is available. For further support on vulnerability remediation, please contact DevNack.com.
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FAQ
The vulnerability in the HV vmbus driver can potentially allow attackers to gain unauthorized access, execute arbitrary code, or cause a denial-of-service condition.
You can use Vulert's playground (https://vulert.com/scanner) to check if your system is affected by this vulnerability. Simply upload your package-lock.json file to the playground, and it will provide real-time alerts for open-source vulnerabilities, including this one.
Yes, the vulnerability has been fixed in Linux Kernel version 5.12.4. It is recommended to update to this version or a later one to mitigate the security risks.
If updating the Linux Kernel is not immediately feasible, a potential workaround is to manually modify the code in the HV vmbus driver to increase the wait time for the VMbus unload operation. Refer to the 'workaround' section for more details.
This vulnerability was discovered by an automated ID intended to aid in the discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven.
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