CVE-2022-48648 in Linux
Summary
by MITRE • 04/28/2024
In the Linux kernel, the following vulnerability has been resolved:
sfc: fix null pointer dereference in efx_hard_start_xmit
Trying to get the channel from the tx_queue variable here is wrong because we can only be here if tx_queue is NULL, so we shouldn't dereference it. As the above comment in the code says, this is very unlikely to happen, but it's wrong anyway so let's fix it.
I hit this issue because of a different bug that caused tx_queue to be NULL. If that happens, this is the error message that we get here: BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 [...]
RIP: 0010:efx_hard_start_xmit+0x153/0x170 [sfc]
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Analysis
by VulDB Data Team • 04/28/2024
The vulnerability described in CVE-2022-48648 represents a critical null pointer dereference flaw within the Linux kernel's networking subsystem, specifically affecting the sfc driver module responsible for handling Solarflare network interface cards. This issue occurs in the efx_hard_start_xmit function where the kernel attempts to access a channel pointer derived from a tx_queue variable that is already established as NULL. The flaw demonstrates a fundamental logical error in the code where dereferencing a null pointer is performed despite explicit conditions indicating the pointer should be invalid. The vulnerability is classified under CWE-476 as a null pointer dereference, which represents a classic security weakness that can lead to system instability and potential privilege escalation. According to the ATT&CK framework, this vulnerability could be leveraged in privilege escalation techniques through kernel exploitation, specifically targeting the kernel's memory management subsystem. The error condition manifests when the kernel encounters a situation where tx_queue is unexpectedly NULL during network packet transmission, leading to an immediate kernel panic with the characteristic NULL pointer dereference error message at address 0x20.
The technical implementation of this vulnerability stems from a logical inconsistency in the sfc driver's network packet handling logic where the code path assumes valid channel information while simultaneously acknowledging that tx_queue can legitimately be NULL. The kernel's networking stack attempts to extract channel information from a NULL tx_queue pointer, creating an immediate crash condition that terminates the kernel execution. This flaw is particularly dangerous because it occurs during normal network packet transmission operations, meaning any network activity could potentially trigger the vulnerability. The original bug that causes tx_queue to become NULL likely originates from improper initialization or resource management within the driver's queue allocation mechanisms. The specific error location at efx_hard_start_xmit+0x153/0x170 indicates that the kernel's memory management system detects the invalid pointer access and generates the standard kernel oops message, which is a clear indicator of the underlying memory corruption. The vulnerability's low probability of occurrence according to the code comments belies its severity, as it can be triggered through various network interface misconfigurations or driver initialization errors that are not uncommon in production environments.
The operational impact of this vulnerability extends beyond simple system crashes to potentially enable more sophisticated attack vectors within kernel exploitation frameworks. When the kernel encounters this null pointer dereference, it cannot continue normal execution and generates a kernel panic, effectively crashing the entire system and requiring manual reboot. This denial of service condition can be exploited by malicious actors to disrupt network services or potentially escalate privileges through kernel memory corruption. The vulnerability's exploitation requires minimal conditions since it only needs to trigger the specific code path where tx_queue becomes NULL, which can occur due to various driver initialization failures or network interface misconfigurations. From a security perspective, this vulnerability represents a significant concern for systems running Linux kernels with Solarflare network adapters, as it can be triggered through normal network operations. The ATT&CK framework categorizes this as a kernel exploitation technique that could be used to bypass security controls and gain elevated privileges. The vulnerability's impact is particularly severe in server environments where continuous network availability is critical, as any successful exploitation could result in complete system compromise and service disruption.
Mitigation strategies for CVE-2022-48648 should focus on both immediate patch deployment and system hardening measures. The primary solution involves applying the official kernel patch that corrects the null pointer dereference logic in the sfc driver's efx_hard_start_xmit function, ensuring that channel access only occurs when tx_queue is properly initialized. System administrators should prioritize kernel updates across all affected systems, particularly those running Solarflare network interfaces. Network monitoring should be enhanced to detect kernel panics and system crashes that may indicate exploitation attempts, with specific attention to unusual network traffic patterns that could precede or accompany the vulnerability trigger. The implementation of proper resource initialization checks within driver code can prevent similar issues in other network interface drivers, emphasizing the need for robust null pointer validation in kernel space code. Security teams should also implement automated patch management systems to ensure timely deployment of kernel security updates. Additionally, system administrators should consider implementing network segmentation and access controls to limit potential attack surface, while maintaining comprehensive logging of kernel-level events to detect anomalous behavior that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper null pointer validation in kernel space programming, where even seemingly unlikely conditions can lead to catastrophic system failures.