CVE-2021-47531 is a vulnerability in the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically within the msm (Qualcomm Snapdragon) driver component. The issue arises from a regression introduced in commit 510410bfc034, which implemented a new method for handling memory mapping (mmap) of GEM (Graphics Execution Manager) objects. Previously, when the mmap function pointer was NULL, the kernel would set specific virtual memory area (VMA) flags including VM_IO and VM_DONTDUMP, which are critical for proper memory handling and stability. However, the new implementation bypassed this default code path, resulting in these flags not being set. This omission led to kernel crashes on devices such as Chromebooks using ARC++ when logging out, due to improper handling of memory mappings. The crash manifests as a kernel paging request failure with detailed ARM64 architecture-specific abort information, indicating a serious memory access violation. The fix involves restoring the VM_IO and VM_DONTDUMP flags to the VMA, which prevents these crashes. Additionally, the patch removes the clearing of VM_PFNMAP as it is no longer necessary, optimizing the code. This vulnerability is not known to be exploited in the wild and affects Linux kernel versions around 5.10 and 5.15 with the relevant backports. The root cause is a subtle but critical memory management regression in the DRM msm driver, impacting system stability on affected hardware platforms.

For European organizations, the impact of CVE-2021-47531 primarily concerns systems running Linux kernels with the affected msm DRM driver, particularly on devices using Qualcomm Snapdragon chipsets such as certain Chromebooks and embedded systems. The vulnerability causes kernel crashes leading to denial of service (DoS) conditions, which can disrupt business operations, especially in environments relying on these devices for critical tasks or user access. While this vulnerability does not directly expose data confidentiality or integrity risks, the resulting system instability can cause service interruptions, data loss due to improper shutdowns, and increased operational costs for recovery and troubleshooting. Organizations deploying Linux-based devices in user-facing roles or embedded applications in industrial or IoT contexts may experience degraded reliability. The lack of known exploits reduces immediate risk, but the potential for future exploitation or triggering of crashes by malicious actors or faulty software remains. European enterprises with Chromebook deployments or embedded Linux devices using Qualcomm hardware should prioritize patching to maintain system stability and avoid operational disruptions.

1. Apply the official Linux kernel patches that restore the VM_IO and VM_DONTDUMP flags in the drm/msm mmap implementation as soon as they are available for your kernel version. 2. For organizations using Chromebooks or embedded devices with Qualcomm Snapdragon chipsets, ensure firmware and kernel updates include this fix. 3. Monitor kernel updates from your Linux distribution vendors and test patches in controlled environments before wide deployment to avoid regressions. 4. Implement robust system monitoring to detect kernel crashes or abnormal reboots that may indicate this or related issues. 5. Where possible, limit user privileges and restrict access to vulnerable devices to reduce the risk of triggering the vulnerability through untrusted code. 6. Maintain up-to-date backups and incident response plans to quickly recover from potential DoS conditions caused by kernel crashes. 7. Engage with hardware and software vendors to confirm the inclusion of this fix in their supported releases and coordinate timely updates.