CVE-2024-35819 is a vulnerability identified in the Linux kernel related to the handling of spinlocks within the soc: fsl: qbman driver component. Specifically, the issue arises from the use of a standard spinlock (cgr_lock) in a context where the Linux kernel's smp_call_function always executes its callback in a hard IRQ context. In PREEMPT_RT (real-time) kernel configurations, spinlocks can sleep, which is incompatible with hard IRQ context execution where sleeping is not allowed. This mismatch can lead to potential deadlocks or system instability because the callback may wait on a sleeping task, which cannot be scheduled in hard IRQ context. The vulnerability became apparent following the commit ef2a8d5478b9, which introduced a call to smp_call_function_single via qman_update_cgr_safe every time a network link goes up or down. The fix involves replacing the standard spinlock with a raw spinlock for cgr_lock to prevent sleeping and ensure proper synchronization in hard IRQ context. Although this bug has existed for some time, it was not evident until the recent code changes triggered the problematic behavior. The affected Linux kernel versions include several commits identified by their hashes, indicating that multiple versions and possibly distributions using these kernel versions are impacted. There are no known exploits in the wild at this time, and no CVSS score has been assigned yet. The vulnerability primarily affects systems using the Freescale (now NXP) DPAA (Data Path Acceleration Architecture) queue manager (qbman) driver, which is common in embedded and networking hardware running Linux kernels with PREEMPT_RT patches or configurations.

For European organizations, the impact of CVE-2024-35819 could be significant in environments relying on Linux-based embedded systems or network infrastructure that utilize the Freescale/NXP DPAA hardware and the qbman driver. This includes telecom providers, industrial control systems, and network equipment manufacturers that deploy Linux kernels with PREEMPT_RT for real-time performance. The vulnerability could lead to system instability, deadlocks, or kernel panics when network links change state, potentially causing denial of service conditions. This disruption could affect critical infrastructure, including telecommunications networks, industrial automation, and data centers that depend on high availability and real-time processing. While no direct exploitation has been reported, the underlying issue could be leveraged by attackers or result in accidental outages, impacting confidentiality, integrity, and availability indirectly by causing system failures or degraded performance. Organizations with real-time Linux deployments in networking or embedded systems should consider this vulnerability a risk to operational continuity.

To mitigate CVE-2024-35819, affected organizations should: 1) Apply the official Linux kernel patches that replace the standard spinlock with a raw spinlock for the cgr_lock in the qbman driver, ensuring compatibility with hard IRQ context execution. 2) Update Linux kernel versions to those that include the fix, typically available through vendor or distribution security updates. 3) For custom or embedded Linux systems, rebuild kernels with the patched qbman driver and thoroughly test network link state changes under PREEMPT_RT configurations. 4) Monitor network interfaces for unusual link flapping or system instability that could indicate triggering of the vulnerability. 5) Implement robust kernel crash and log monitoring to detect potential deadlocks or panics related to this issue. 6) Coordinate with hardware vendors (e.g., NXP) for firmware or driver updates that may complement kernel patches. 7) Where possible, limit exposure of affected embedded devices to untrusted networks to reduce risk of exploitation or accidental triggering. 8) Maintain regular backups and incident response plans to quickly recover from potential denial of service events caused by this vulnerability.