CVE-2021-47529

What it actually does

Memory leak in iwlwifi driver error path: allocated reduce_power_data structures are not freed on invalid TLV length or allocation failure, causing gradual kernel memory exhaustion.

Why it matters to the business

Affected Linux systems may experience increasing memory pressure leading to performance degradation or denial-of-service conditions after repeated error-triggering events in wireless hardware initialization.

How an attack unfolds

An attacker with local access supplies malformed or adversarial wireless configuration data that triggers the error-handling path in reduce_power_data allocation, leaving the previously allocated memory unfreed and accumulating over multiple invocations.

How to fix it

Apply the upstream fix for the memory-leak error path in iwlwifi; update to a Linux kernel version containing the resolution of the reduce_power_data leak (post-2021-47529 commit) or backport the error-handling free before return.

How to confirm the fix worked

Confirm kernel source contains the added kfree on error return in the reduce_power_data path; run memory-leak detection tools during driver error injection; verify wireless initialization succeeds without unbounded allocation growth.

Typical attack path

1. Obtain local user access on target Linux system with iwlwifi hardware
2. Trigger wireless driver initialization or power-reduction TLV parsing with invalid length or under memory pressure
3. Cause repeated allocation failures or TLV errors without triggering normal cleanup
4. Observe progressive kernel memory depletion until system impact occurs

How to detect it

Review kernel logs for repeated iwlwifi error paths involving TLV length or allocation failures; use slabtop or kmemleak to observe growing allocations in reduce_power_data structures; correlate with wireless interface bring-up events.

What your security team should do

• Prioritize kernel updates on systems using Intel wireless hardware
• Monitor kernel memory usage and slab allocator statistics for iwlwifi objects
• Apply the fix during next maintenance window given the 878-day publication age
• Restrict local access where possible until patched