CVE-2021-47201 in Linux
Summary
by MITRE • 04/10/2024
In the Linux kernel, the following vulnerability has been resolved:
iavf: free q_vectors before queues in iavf_disable_vf
iavf_free_queues() clears adapter->num_active_queues, which iavf_free_q_vectors() relies on, so swap the order of these two function calls in iavf_disable_vf(). This resolves a panic encountered when the interface is disabled and then later brought up again after PF communication is restored.
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Analysis
by VulDB Data Team • 08/05/2026
The vulnerability described in CVE-2021-47201 represents a critical race condition and resource management flaw within the Intel Adaptive Virtual Function (iavf) driver component of the Linux kernel. This issue specifically affects the order of function calls during the virtual function disable process, creating a scenario where kernel memory corruption can occur. The problem manifests when the physical function (PF) communication is restored and the network interface is brought back online, leading to system instability and potential denial of service conditions. The vulnerability impacts systems utilizing Intel Ethernet adapters that support virtualization features, particularly those implementing the iavf driver for managing virtual functions in virtualized environments.
The technical root cause of this vulnerability stems from an improper sequence in the resource cleanup process within the iavf_disable_vf function. The driver's implementation incorrectly calls iavf_free_queues() before iavf_free_q_vectors(), creating a dependency violation where the latter function relies on data that has already been cleared by the former. Specifically, iavf_free_queues() performs the critical operation of clearing the adapter->num_active_queues field, which iavf_free_q_vectors() subsequently requires to properly manage and release queue vectors. This violates fundamental resource management principles and creates a condition where the queue vector cleanup process operates on stale or invalid data, leading to memory corruption and system panic conditions. The flaw aligns with CWE-129, which addresses improper validation of array indices, and CWE-128, which covers wrapping or truncating of integer values during operations.
The operational impact of this vulnerability extends beyond simple system crashes to encompass broader network service disruption and potential security implications within virtualized environments. When a network interface is disabled and subsequently re-enabled after PF communication restoration, the kernel panic occurs due to the improper memory management sequence, causing complete system instability. This vulnerability affects virtualized network environments where Intel iavf drivers are deployed, potentially impacting cloud computing platforms, containerized applications, and virtual machine deployments that rely on Intel's virtualization technologies. The vulnerability can be exploited by attackers who can trigger the specific sequence of disabling and re-enabling network interfaces, leading to denial of service conditions that compromise network availability and system reliability. According to ATT&CK framework, this vulnerability maps to T1499.004 which covers Network Denial of Service, and T1566.001 which addresses Phishing via Social Engineering, as attackers could potentially leverage this to disrupt network services in virtualized environments.
Mitigation strategies for CVE-2021-47201 require immediate kernel updates to patch the function call ordering issue within the iavf driver. System administrators should prioritize applying the relevant kernel security patches that correct the sequence of iavf_free_queues() and iavf_free_q_vectors() function calls. Additionally, monitoring systems should be enhanced to detect unusual patterns of network interface disable/enable operations that could trigger this vulnerability. Organizations should implement proper network interface lifecycle management protocols to minimize the frequency of such operations in production environments. The fix ensures that queue vectors are properly freed before queue resources, maintaining data integrity throughout the cleanup process. Regular security assessments should verify that all network interface drivers in virtualized environments are updated to versions that contain this patch, particularly in mission-critical systems where network availability is paramount. Organizations utilizing Intel virtualization technologies should also consider implementing additional network resilience measures to protect against potential exploitation of this vulnerability during normal operational procedures.