CVE-2024-42307

What it actually does

Null pointer dereference in destroy_workqueue call during error unwinding in init_cifs when serverclose_wq allocation fails or is skipped due to incorrect ordering of cleanup steps in fs/smb/client/cifsfs.c.

Why it matters to the business

Kernel instability or crash on systems using the CIFS/SMB client under rare initialization failure conditions, potentially affecting file sharing workloads; low prevalence reduces overall operational risk despite wide Linux kernel deployment.

How an attack unfolds

An attacker would need to trigger a specific failure path during CIFS module initialization that leaves serverclose_wq unallocated, then cause the error handler to invoke destroy_workqueue on the null pointer; no public exploits or successful campaigns observed given the constrained trigger conditions and low EPSS.

How to fix it

Upgrade Linux kernel to version 6.1.103 or apply commit 6018971710fdc7739f8655c1540832b4bb903671 (or equivalent stable backport) in the cifs module; rebuild and reboot affected systems.

How to confirm the fix worked

Verify running kernel version is at or above the fixed release; inspect fs/smb/client/cifsfs.c around line 1981 for the corrected cleanup ordering; run static analysis tools such as Smatch on the patched source.

Typical attack path

1. Identify or induce an error condition during cifsfs initialization that skips serverclose_wq allocation
2. Force execution of the incorrect error-path ordering in init_cifs
3. Trigger destroy_workqueue on the uninitialized null pointer
4. Cause kernel panic or memory corruption

How to detect it

Examine kernel logs for oops or null pointer dereference traces referencing destroy_workqueue and init_cifs during CIFS module load; no widespread exploitation indicators reported.

What your security team should do

• Prioritize kernel upgrades on systems with active CIFS mounts within standard patch windows given low EPSS and absence from KEV
• Monitor upstream stable kernel releases for additional CIFS-related fixes
• Review CIFS error handling and workqueue usage in custom or older kernel builds