CVE-2023-54119

What it actually does

A race between inotify_freeing_mark and inotify_handle_inode_event allows the latter to observe a watch descriptor already reset to -1 and deliver that invalid value to userspace, confusing inotify listeners.

Why it matters to the business

File-monitoring applications on Linux systems may receive malformed events, leading to crashes, missed notifications, or incorrect behavior in tools that rely on inotify for change detection across a wide range of servers and containers.

How an attack unfolds

An attacker with local access triggers concurrent mark removal and event generation to force the kernel to report an invalid watch descriptor, disrupting userspace processes that depend on accurate inotify events.

How to fix it

Upgrade the Linux kernel to a version containing commit 8fb33166aed888769ea63d6af49515893f8a1f14 or any later stable release that includes the fix.

How to confirm the fix worked

Confirm the running kernel contains commit 8fb33166aed888769ea63d6af49515893f8a1f14; exercise inotify under concurrent mark removal workloads to verify no invalid watch descriptors are reported.

Typical attack path

1. Obtain local execution on a vulnerable Linux system
2. Create conditions that race inotify mark freeing against event delivery
3. Observe or induce userspace confusion from the invalid watch descriptor value

How to detect it

Inspect application logs for unexpected negative or invalid watch descriptor values; review kernel logs around inotify events for signs of mark-removal races; no widespread exploitation artifacts are known.

What your security team should do

• Apply the kernel update containing commit 8fb33166aed888769ea63d6af49515893f8a1f14 as soon as packages are available
• Prioritize patching on systems with heavy inotify usage such as containers and file servers
• Review inotify-dependent applications for defensive handling of unexpected watch descriptors