CVE-2021-47073

What it actually does

Unconditional driver_unregister call in exit_dell_smbios_wmi() without matching the conditional register in init_dell_smbios_wmi() triggers kernel warning and oops on module unload.

Why it matters to the business

Kernel instability and potential system crash on Dell hardware when the dell_smbios module is removed, increasing operational risk during maintenance or driver updates.

How an attack unfolds

An attacker with local access issues rmmod on the dell_smbios module to trigger the unconditional unregister path and induce a kernel oops, disrupting system availability.

How to fix it

Update to a Linux kernel version containing the fix that conditions the unregister on the same check as the register; rebuild and deploy the corrected kernel module.

How to confirm the fix worked

Confirm the patch is present by inspecting drivers/platform/x86/dell-smbios-wmi.c for conditional unregister logic matching the register path, then test module load/unload on Dell hardware.

Typical attack path

1. Obtain local shell or sufficient privileges on affected Dell system
2. Execute rmmod dell_smbios or equivalent module unload
3. Trigger the mismatched unregister logic causing kernel oops

How to detect it

Review kernel logs for 'Unexpected driver unregister!' warnings during module cleanup; correlate with dell_smbios module activity in dmesg or syslog.

• Unexpected driver unregister!
• WARNING: CPU.*driver_unregister
• cleanup_module.*dell_smbios

What your security team should do

• Prioritize kernel updates on Dell systems using the dell-smbios-wmi driver
• Monitor module unload events in production kernels for unexpected oops
• Restrict local module unload permissions where feasible