CVE-2023-0469

What it actually does

Use-after-free condition in io_uring/filetable.c during io_install_fixed_file cleanup allows a local process to trigger invalid memory access, resulting in kernel panic or denial of service.

Why it matters to the business

Linux systems using io_uring may experience unexpected crashes or service unavailability when local workloads exercise the affected code path, increasing operational downtime risk for compute-heavy environments.

How an attack unfolds

An attacker with local user privileges crafts io_uring operations that exercise the filetable installation path; during subsequent cleanup the freed structure is referenced, causing the kernel to fault and terminate the process or panic the system.

How to fix it

Upgrade the Linux kernel to a version containing commit 830b3c68c1fb1e9176028d02ef86f3cf76aa2476 or later; rebuild and reboot with the patched kernel; if immediate patching is not possible, restrict untrusted local accounts from using io_uring via seccomp or kernel module blacklisting.

How to confirm the fix worked

Verify the running kernel contains commit 830b3c68c1fb1e9176028d02ef86f3cf76aa2476 via git log or uname output; test io_uring workloads that previously triggered the flaw and confirm absence of use-after-free warnings in dmesg or kernel logs.

Typical attack path

1. Obtain local shell or unprivileged process execution on target host
2. Issue io_uring setup, register files, and submit operations that trigger io_install_fixed_file
3. Force or wait for cleanup path that reuses the dangling file table entry
4. Observe resulting kernel oops or system hang confirming denial of service

How to detect it

Review kernel logs (dmesg, /var/log/kern.log) for oops or panic messages referencing io_uring/filetable.c or io_install_fixed_file; correlate with process creation events that use io_uring syscalls; look for repeated crashes on hosts running vulnerable kernels.

• io_install_fixed_file
• io_uring/filetable.c
• use-after-free.*io_uring

What your security team should do

• Apply the referenced kernel commit immediately on all systems exposing io_uring to untrusted local users
• Monitor kernel crash reports for io_uring related oopses as a temporary detection measure
• Limit io_uring usage via seccomp filters for containers and user namespaces until patches are deployed