CVE-2024-40979: 
Linux Kernel vulnerability analysis and mitigation

CVE-2024-40979 affects the Linux kernel's ath12k WiFi driver, specifically related to QMI target memory handling during system resume. The vulnerability was discovered and disclosed on July 12, 2024. The issue affects systems using the ath12k wireless driver with WCN7850 hardware (Kernel Git).

The vulnerability occurs when QMI target memory is not properly handled during system resume, specifically in cases where DMA remap is not supported. During resume, the firmware requests two large memory segments, but when allocation fails, the ath12k_qmi_free_target_mem_chunk() function attempts to free memory segments with incorrect sizes. This mismatch between allocated and freed memory sizes (524288 bytes vs 8454144 bytes) leads to a kernel crash (Kernel Git).

When exploited, this vulnerability results in a kernel crash, manifesting as a 'Bad page state' error in the kworker process. The issue specifically affects systems during the resume process from suspend state, potentially causing system instability and denial of service (Kernel Git).

The vulnerability is triggered during normal system operation, specifically during the resume process from suspend state. It requires no special privileges to trigger, as it occurs during standard power management operations (Kernel Git).

The issue has been fixed by adding prev_size to the target_mem_chunk structure and caching real segment size in it. The fix ensures that prev_size instead of current size is passed to dma_free_coherent(), preventing the freeing of unexpected memory. Additionally, the patch implements m3 buffer reuse similar to the ath11k driver (Kernel Git).