CVE-2023-52486 is a vulnerability identified in the Linux kernel's Direct Rendering Manager (DRM) subsystem, specifically within the framebuffer (fb) reference handling during asynchronous page flips. The issue arises in the drm_mode_page_flip_ioctl() function, where, upon encountering a deadlock after the framebuffer lookup, the code attempts to unreference (unref) the framebuffer and then retries the operation. However, the framebuffer pointer is not reset to NULL after the unref operation. Consequently, if another error occurs during the retry before a new framebuffer lookup, the code erroneously unreferences the same framebuffer again without having acquired a new reference. This double unref leads to the framebuffer being freed while still in use, causing use-after-free conditions. The vulnerability was notably reproducible on Intel DG2 graphics hardware when performing asynchronous flips with the CONFIG_DEBUG_WW_MUTEX_SLOWPATH=y kernel configuration enabled. The immediate symptom observed was drm_closefb() entering a busy loop while traversing the framebuffer list, which was later debugged to cause a kernel oops (crash). This flaw can lead to kernel instability, crashes, and potentially exploitable conditions due to use-after-free in kernel memory management related to graphics buffers. No known exploits are reported in the wild as of the publication date. The vulnerability affects Linux kernel versions identified by the commit hash 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 and presumably earlier versions lacking the fix. The patch involves resetting the framebuffer pointer to NULL after unreferencing it to prevent multiple unrefs of the same framebuffer reference during error handling and retries.

For European organizations relying on Linux-based systems with DRM-enabled graphics subsystems, especially those using Intel DG2 or similar hardware, this vulnerability poses a risk of kernel crashes and system instability. This can impact servers, workstations, and embedded systems running Linux kernels vulnerable to this flaw. The use-after-free condition could potentially be leveraged by a local attacker or malicious process with the ability to trigger asynchronous page flips to cause denial of service (system crashes) or possibly escalate privileges if combined with other vulnerabilities. Critical infrastructure, research institutions, and enterprises using Linux for graphical workloads or GPU-accelerated applications may experience disruptions. Although no public exploits exist currently, the vulnerability's presence in the kernel graphics stack means that systems performing graphics-intensive operations or running containerized workloads with GPU passthrough could be affected. The impact on confidentiality is limited, but integrity and availability could be compromised due to kernel panics or memory corruption. Given the kernel-level nature, recovery from crashes may require system reboots, affecting operational continuity.

European organizations should promptly update their Linux kernels to versions that include the fix for CVE-2023-52486. This involves applying the patch that resets the framebuffer pointer to NULL after unreferencing it to prevent double unref errors. For environments where immediate kernel upgrades are challenging, organizations should consider disabling asynchronous page flips or related DRM features if feasible, especially on systems using Intel DG2 or similar GPUs. Monitoring kernel logs for drm_closefb() busy loops or oops messages can help detect attempts to trigger this vulnerability. Additionally, restricting unprivileged user access to DRM ioctls and limiting the ability to perform asynchronous flips can reduce exploitation risk. Organizations should also ensure kernel debugging features like CONFIG_DEBUG_WW_MUTEX_SLOWPATH are disabled in production to avoid performance impacts and potential exposure. Regularly auditing and updating GPU drivers and firmware is recommended. Finally, integrating this vulnerability into vulnerability management and incident response plans will help maintain awareness and readiness.