CVE-2024-57942

What it actually does

The flaw leaves the folio_queue entry uncleared after marking folios with PG_private_2 in netfs_unlock_read_folio(), causing netfs_pgpriv2_write_to_the_cache() to hang while scanning the list during ceph cache write-back on fsc mounts.

Why it matters to the business

Write operations to Ceph filesystems with client caching trigger kernel hangs, disrupting availability and requiring reboots on affected Linux systems; listed package prevalence is low but kernel exposure is broad.

How an attack unfolds

An attacker with local access mounts a Ceph filesystem using the fsc option, performs writes that invoke netfs_unlock_read_folio() with cache copy intent, and triggers the uncleared folio_queue leading to a hang; unrelated kernel privilege-escalation actors have been observed targeting similar Linux kernel surfaces.

How to fix it

Apply the upstream netfs fix or vendor kernel update; for the listed Red Hat packages upgrade ocaml, ocaml-camlp4, ocaml-compiler-libs and related components to the versions fixed in 0:4.01.0-22.7.el7_2 on both client and computenode variants.

How to confirm the fix worked

Confirm kernel or package version matches the fixed release, reproduce the original ceph fsc write workload, and verify no hang occurs in netfs_pgpriv2_write_to_the_cache().

Typical attack path

1. Obtain local user access on a Linux system with Ceph client
2. Mount Ceph filesystem with -o fsc to enable cache
3. Perform file writes that exercise netfs write-begin path
4. Trigger folio marking and unlock sequence to hang the cache writer thread

How to detect it

Review kernel logs and dmesg for netfs or folio_queue related stalls during Ceph writes; correlate with process activity on ceph-mounted paths; threat actor context from similar kernel CVEs may appear in exploit attempts.

What your security team should do

• Prioritize kernel and ocaml package updates on all systems exposing Ceph mounts
• Disable fsc cache option until patched if immediate upgrade is not feasible
• Monitor for kernel hang reports on Ceph clients and schedule validation testing