CVE-2023-53519

What it actually does

Data race on the num_rdy field in v4l2_m2m_buf_queue allowing concurrent unsynchronized read/write access from v4l2_m2m_num_src_bufs_ready and v4l2_m2m_num_dst_bufs_ready, resulting in inconsistent buffer counts and potential kernel memory corruption or panic under load.

Why it matters to the business

Linux systems performing video encoding, decoding or media transcoding via V4L2 memory-to-memory devices may experience intermittent kernel crashes or hangs, disrupting workloads on servers, embedded devices and container-optimized OS images.

How an attack unfolds

An attacker with local access triggers concurrent calls to v4l2_m2m_buf_queue while the num_rdy counters are read, exploiting the missing lock; repeated triggering under KCSAN or high concurrency can induce undefined behavior leading to denial of service. Related container privilege-escalation techniques observed in VMSCAPE and similar Linux kernel issues may be adapted to reach this race.

How to fix it

Update the Linux kernel to the commit 690dd4780b3f4d755e4e7883e8c3d1b5052f6bf2 or later stable releases that include the lock protecting num_rdy; rebuild and deploy the fixed kernel across all affected hosts and container images.

How to confirm the fix worked

Verify the running kernel contains commit 690dd4780b3f4d755e4e7883e8c3d1b5052f6bf2 via git log or uname; re-run KCSAN on the v4l2-mem2mem driver and confirm absence of the data-race report on num_rdy.

Typical attack path

1. Obtain local user or container access on a Linux host using V4L2 mem2mem drivers
2. Open and queue buffers to a v4l2-mem2mem context from multiple threads or processes
3. Trigger concurrent execution of v4l2_m2m_buf_queue and the num_*_bufs_ready helpers
4. Observe or force kernel instability via the resulting data race

How to detect it

Search kernel logs and KCSAN reports for strings referencing v4l2_m2m_buf_queue and data-race on num_rdy; inspect crash dumps for concurrent access patterns in the media subsystem.

• BUG: KCSAN: data-race in v4l2_m2m_buf_queue
• v4l2_m2m_num_src_bufs_ready
• v4l2_m2m_num_dst_bufs_ready
• read-write to .*num_rdy

What your security team should do

• Prioritize kernel upgrade to the fixed commit on all systems exposing V4L2 mem2mem interfaces
• Monitor for KCSAN or BUG reports mentioning v4l2_m2m_buf_queue in production logs
• Restrict untrusted local access and container workloads until patches are applied