CVE-2021-47631 is a vulnerability identified in the Linux kernel specifically affecting ARM architecture platforms using the davinci SoC family, notably the da850-evm board. The issue arises from a NULL pointer dereference in the da850_evm_config_emac() function during the initialization phase of the Ethernet MAC (emac) driver. The root cause is that the emac_pdata pointer within the soc_info structure is NULL because davinci_soc_info is only populated for davinci machines, but the da850_evm_config_emac() function is invoked on all machines via device_initcall(). This leads to an attempt to dereference a NULL pointer when assigning the rmii_en field, causing a kernel panic and system crash. The problem is triggered during boot, particularly when using multi_v5_defconfig in QEMU under the palmetto-bmc machine, but it can affect real hardware running affected kernel versions. The vulnerability is due to improper conditional checks before dereferencing pointers, and the fix involves moving the rmii_en assignment below a machine check to ensure it only executes on supported SoCs. This vulnerability does not have known exploits in the wild and lacks a CVSS score, but it can cause denial of service by crashing the kernel during boot or initialization.

For European organizations, the impact of CVE-2021-47631 is primarily related to availability. Systems running affected Linux kernel versions on ARM-based davinci SoCs, such as da850-evm boards, may experience kernel panics and boot failures, leading to downtime. This can disrupt embedded systems, industrial control devices, or specialized hardware platforms using these SoCs. While the vulnerability does not directly expose confidentiality or integrity risks, the denial of service caused by kernel crashes can affect operational continuity, especially in critical infrastructure or manufacturing environments where embedded Linux devices are common. Since the vulnerability occurs early in the boot process, recovery may require physical access or remote management capabilities to restore system functionality. The lack of known exploits reduces immediate risk, but unpatched systems remain vulnerable to accidental crashes or targeted disruption attempts.

To mitigate CVE-2021-47631, organizations should: 1) Identify and inventory devices running Linux kernels with the affected ARM davinci SoC support, particularly da850-evm or similar platforms. 2) Apply the official Linux kernel patches that move the rmii_en assignment below the machine check in da850_evm_config_emac(), ensuring the pointer dereference only occurs on supported SoCs. 3) Update to a Linux kernel version that includes this fix, preferably from a trusted vendor or distribution with backported patches. 4) For embedded or specialized devices where kernel updates are challenging, consider recompiling the kernel with the patch or disabling the problematic driver if not required. 5) Implement monitoring to detect kernel panics or boot failures indicative of this issue. 6) Maintain secure remote management and recovery procedures to restore affected devices without physical access. 7) Test updates in controlled environments to avoid disruptions in production systems.