CVE-2023-54285

What it actually does

Unsigned long value from folio_next_index() left-shifted by PAGE_SHIFT can overflow on 32-bit systems during iomap_write_delalloc_scan, leading to incorrect folio range calculations and potential memory corruption or kernel misbehavior in delayed allocation write paths.

Why it matters to the business

On 32-bit Linux systems, local users or processes could trigger kernel instability, crashes, or data corruption during file writes involving delayed allocation, increasing downtime and integrity risks in environments relying on older kernels.

How an attack unfolds

An attacker with local access crafts operations that invoke iomap_write_delalloc_scan with folio configurations causing the overflow calculation on 32-bit kernels, resulting in out-of-bounds or incorrect memory access during delalloc scanning.

How to fix it

Upgrade the Linux kernel to version 6.1.162 or later, or apply the commit 0c6cf409093f307ee05114f834516730c0da5b21 in the stable tree; rebuild and reboot affected systems.

How to confirm the fix worked

Confirm kernel version is at or above 6.1.162; review dmesg or kernel logs for absence of related iomap warnings; test delalloc write workloads on 32-bit builds to ensure no overflow symptoms.

Typical attack path

1. Obtain local user or process access on a 32-bit Linux system
2. Trigger file write operations that engage the delayed allocation path in the iomap subsystem
3. Force folio_next_index calculations that exceed 32-bit bounds after PAGE_SHIFT
4. Cause the kernel to miscalculate folio ranges leading to corruption or crash

How to detect it

Review kernel logs and audit trails for unexpected iomap or folio-related errors on 32-bit systems; no specific post-exploitation artifacts are publicly documented.

What your security team should do

• Prioritize patching 32-bit Linux systems to fixed kernel versions within maintenance windows
• Audit workloads using delayed allocation on 32-bit hardware for stability issues
• Monitor EPSS and exploit maturity indicators for any future increases in risk