CVE-2024-56560

What it actually does

Incorrect alignment assumption in slab create_cache() for freeptr_t on architectures where unsigned long minimum alignment is smaller than its size (such as m68k at 2 bytes) causes __kmem_cache_create_args to fail with -EINVAL when creating slabs like io_kiocb, triggering kernel panic during subsystem initialization.

Why it matters to the business

Systems running affected kernels on m68k hardware experience boot failures or crashes during io_uring initialization, leading to complete loss of availability on those platforms; low prevalence reduces overall operational risk but requires targeted patching for any affected embedded or legacy deployments.

How an attack unfolds

An attacker with the ability to trigger kernel initialization on an m68k system (for example via crafted boot or module load) causes the slab creation failure due to the overly strict alignment check, resulting in panic; no remote unauthenticated vector or privilege escalation is present.

How to fix it

Update to a fixed kernel containing commit 8b5aea5e5186733fa4e5aa4293b0a65a933f1a16 or later; for affected Ubuntu packages apply the webkit2gtk 2.14.2-0ubuntu0.16.04.1 update if applicable to the distribution build.

How to confirm the fix worked

Boot the updated kernel on m68k hardware and confirm successful creation of the io_kiocb slab without -EINVAL errors in dmesg; verify the presence of the relaxed alignment check in mm/slab_common.c.

Typical attack path

1. Identify or gain access to m68k Linux system running vulnerable kernel version
2. Trigger io_uring initialization path during boot or early userspace
3. Observe slab creation failure and resulting kernel panic

How to detect it

Examine kernel boot logs and dmesg for panic messages referencing __kmem_cache_create_args failure when creating the io_kiocb slab on m68k; no post-exploitation artifacts are expected because the flaw manifests as an immediate crash.

What your security team should do

• Prioritize kernel updates for any m68k deployments within standard change windows
• Monitor boot logs on m68k systems for slab creation panics until patched
• Review downstream package builds that incorporate the affected kernel code for backports