CVE-2023-2430

What it actually does

Missing lock in io_cqring_event_overflow() within io_uring.c creates a race condition under IOPOLL that allows a local user to trigger kernel panic or crash, resulting in denial of service.

Why it matters to the business

Local users on affected Linux systems can force reboots or downtime, interrupting workloads and availability on any machine where untrusted accounts exist.

How an attack unfolds

An attacker with local user privileges invokes io_uring operations that exercise the IOPOLL path, times concurrent accesses to hit the unprotected overflow handling, and causes the kernel to crash.

How to fix it

Upgrade the Linux kernel to a version that includes commit e12d7a46f65ae4b7d58a5e0c1cbfa825cf8; rebuild and reboot with the patched kernel image.

How to confirm the fix worked

Verify the running kernel contains commit e12d7a46f65ae4b7d58a5e0c1cbfa825cf8 via git log or version string; attempt controlled reproduction of the race in a lab environment to confirm the crash no longer occurs.

Typical attack path

1. Gain local shell or process execution as a non-root user
2. Load or write code that opens an io_uring instance with IOPOLL enabled
3. Trigger concurrent submission and completion events to race the overflow path
4. Observe kernel panic and system reboot

How to detect it

Search kernel logs and dmesg for oops or panic entries referencing io_cqring_event_overflow or io_uring; monitor process activity for unexpected io_uring usage patterns.

• io_cqring_event_overflow
• io_uring.*IOPOLL
• kernel: BUG: unable to handle kernel NULL pointer dereference.*io_uring

What your security team should do

• Apply the kernel patch containing commit e12d7a46f65ae4b7d58a5e0c1cbfa825cf8 on all systems as soon as possible
• Disable io_uring for untrusted users via kernel configuration or seccomp where feasible
• Audit systems for local accounts that could abuse the flaw and apply least-privilege controls