CVE-2023-54156 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
sfc: fix crash when reading stats while NIC is resetting
efx_net_stats() (.ndo_get_stats64) can be called during an ethtool selftest, during which time nic_data->mc_stats is NULL as the NIC has been fini'd. In this case do not attempt to fetch the latest stats from the hardware, else we will crash on a NULL dereference: BUG: kernel NULL pointer dereference, address: 0000000000000038 RIP efx_nic_update_stats abridged calltrace: efx_ef10_update_stats_pf efx_net_stats dev_get_stats dev_seq_printf_stats Skipping the read is safe, we will simply give out stale stats. To ensure that the free in efx_ef10_fini_nic() does not race against efx_ef10_update_stats_pf(), which could cause a TOCTTOU bug, take the efx->stats_lock in fini_nic (it is already held across update_stats).
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Analysis
by VulDB Data Team • 01/03/2026
The vulnerability CVE-2023-54156 represents a critical null pointer dereference issue within the Linux kernel's sfc driver, specifically affecting the Solarflare network interface controller implementation. This flaw manifests when the efx_net_stats() function, which serves as the .ndo_get_stats64 callback for network device statistics, attempts to access hardware statistics during a NIC reset operation. The underlying issue stems from the timing of concurrent operations where the ethtool selftest command triggers a NIC fini operation while simultaneously invoking the statistics reading interface, creating a race condition that leads to system crashes.
The technical implementation of this vulnerability involves the efx_nic_update_stats function which attempts to dereference the nic_data->mc_stats structure pointer that has already been freed during the NIC finalization process. When the NIC is in the midst of resetting, the mc_stats field becomes NULL, yet the efx_net_stats() function does not properly validate this condition before attempting to access the hardware statistics registers. The crash occurs at memory address 0x0000000000000038, which corresponds to the mc_stats->stats field, demonstrating a classic null pointer dereference pattern that results in kernel panic and system instability. This issue directly maps to CWE-476 Null Pointer Dereference, a fundamental security weakness that can lead to denial of service and potential privilege escalation.
The operational impact of this vulnerability extends beyond simple system crashes to encompass broader network reliability concerns and potential service disruption. When the kernel encounters this condition during active network monitoring or management operations, the entire system becomes unstable, requiring manual intervention to recover from the kernel panic. Network administrators operating systems with affected kernel versions face the risk of unexpected downtime during routine maintenance activities such as ethtool selftests, which are standard procedures for network interface diagnostics. The vulnerability affects systems using Solarflare network controllers and demonstrates how improper resource management during device lifecycle operations can create exploitable conditions. According to ATT&CK framework, this represents a privilege escalation vector through system instability (T1499.004) and can be leveraged to cause denial of service (T1499.001) attacks that compromise system availability.
The resolution for CVE-2023-54156 implements a defensive programming approach that addresses both the immediate null pointer dereference and the underlying race condition. The fix introduces proper validation checks within the efx_net_stats() function to detect when nic_data->mc_stats is NULL and gracefully skips the hardware statistics update rather than attempting to access freed memory. This approach ensures that stale statistics are returned instead of causing system crashes, maintaining system stability while preserving the availability of statistical information. The solution also addresses the temporal consistency issue by ensuring proper locking mechanisms are maintained during the NIC finalization process, specifically by taking the efx->stats_lock within the fini_nic function. This prevents the time-of-check to time-of-use (TOCTOU) race condition where the statistics update function could access freed memory after the finalization process has begun but before it completes. The fix demonstrates proper resource management practices that align with security best practices for kernel development and system reliability. The implementation follows established patterns for handling concurrent access to shared resources in kernel space, ensuring that the statistics update operations maintain consistency with the device lifecycle management operations while preserving system stability and preventing unauthorized access to freed memory regions.