CVE-2021-47422

What it actually does

The flaw is a memory leak in the Nouveau KMS driver where single_open() allocates an 'op' structure that is never freed because single_release() is omitted from the file operations.

Why it matters to the business

Prolonged local use of affected graphics interfaces gradually consumes kernel memory, risking system instability, degraded performance, or crashes on Linux systems using the open-source Nouveau driver for NVIDIA hardware.

How an attack unfolds

An attacker with local access repeatedly opens and closes specific debug or proc files exposed by the nv50 KMS code; each open allocates memory that is never released, slowly exhausting resources until the system becomes unusable.

How to fix it

Apply a Linux kernel update containing the upstream fix that replaces the release handler with single_release() in the drm/nouveau/kms/nv50- code paths.

How to confirm the fix worked

Inspect the patched kernel source or running module to confirm single_release() is registered for the affected file operations; test by exercising the interfaces and verifying no incremental memory growth.

Typical attack path

1. Obtain local user access on a target Linux system
2. Locate the Nouveau KMS file interfaces under debugfs or similar
3. Repeatedly open and close those files in a loop
4. Observe progressive kernel memory depletion and system impact

How to detect it

Review kernel logs and memory accounting for repeated allocations tied to Nouveau file open operations without matching releases; correlate with user activity on debugfs entries.

What your security team should do

• Schedule kernel upgrades for all systems using the Nouveau driver
• Monitor kernel memory statistics on graphics-enabled hosts
• Evaluate migration to the proprietary NVIDIA driver where feasible