CVE-2024-40979 in Linux
Summary
by MITRE • 07/12/2024
In the Linux kernel, the following vulnerability has been resolved:
wifi: ath12k: fix kernel crash during resume
Currently during resume, QMI target memory is not properly handled, resulting in kernel crash in case DMA remap is not supported:
BUG: Bad page state in process kworker/u16:54 pfn:36e80 page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x36e80 page dumped because: nonzero _refcount Call Trace: bad_page free_page_is_bad_report __free_pages_ok __free_pages dma_direct_free dma_free_attrs ath12k_qmi_free_target_mem_chunk ath12k_qmi_msg_mem_request_cb
The reason is: Once ath12k module is loaded, firmware sends memory request to host. In case DMA remap not supported, ath12k refuses the first request due to failure in allocating with large segment size:
ath12k_pci 0000:04:00.0: qmi firmware request memory request ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 7077888 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 8454144 ath12k_pci 0000:04:00.0: qmi dma allocation failed (7077888 B type 1), will try later with small size ath12k_pci 0000:04:00.0: qmi delays mem_request 2 ath12k_pci 0000:04:00.0: qmi firmware request memory request
Later firmware comes back with more but small segments and allocation succeeds:
ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 262144 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 524288 ath12k_pci 0000:04:00.0: qmi mem seg type 4 size 65536 ath12k_pci 0000:04:00.0: qmi mem seg type 1 size 524288
Now ath12k is working. If suspend is triggered, firmware will be reloaded during resume. As same as before, firmware requests two large segments at first. In ath12k_qmi_msg_mem_request_cb() segment count and size are assigned:
ab->qmi.mem_seg_count == 2 ab->qmi.target_mem[0].size == 7077888
ab->qmi.target_mem[1].size == 8454144
Then allocation failed like before and ath12k_qmi_free_target_mem_chunk() is called to free all allocated segments. Note the first segment is skipped because its v.addr is cleared due to allocation failure:
chunk->v.addr = dma_alloc_coherent()
Also note that this leaks that segment because it has not been freed.
While freeing the second segment, a size of 8454144 is passed to dma_free_coherent(). However remember that this segment is allocated at the first time firmware is loaded, before suspend. So its real size is 524288, much smaller than 8454144. As a result kernel found we are freeing some memory which is in use and thus cras ---truncated---
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Analysis
by VulDB Data Team • 09/17/2025
The vulnerability described in CVE-2024-40979 affects the Linux kernel's wireless subsystem, specifically within the ath12k driver used for Qualcomm Wi-Fi 6E chipsets. This issue manifests as a kernel crash during system resume operations, particularly when the system lacks support for DMA remapping capabilities. The root cause stems from improper handling of QMI target memory during the resume process, which leads to memory management inconsistencies and ultimately system instability. The flaw occurs when the wireless driver attempts to reallocate memory segments previously acquired during initial firmware loading, but fails to correctly account for the actual memory sizes allocated during the first firmware initialization.
The technical implementation of this vulnerability involves a complex interaction between firmware communication protocols, memory allocation strategies, and DMA handling within the kernel's memory management subsystem. During normal operation, the ath12k driver receives memory requests from firmware that initially fail due to insufficient large segment allocation capabilities. The driver then retries with smaller segments, successfully allocating memory for the first firmware load cycle. However, during system suspend and resume, the same firmware requests are processed again, but the driver fails to properly track the actual memory segment sizes that were originally allocated. This mismatch occurs because the driver maintains a cached view of memory segment information that does not reflect the actual allocation sizes used during the initial firmware load, leading to incorrect memory deallocation parameters.
The operational impact of this vulnerability is significant, as it can cause complete system crashes during the resume phase, effectively making suspend and resume functionality unreliable for systems using the affected wireless hardware. This vulnerability directly relates to CWE-121, which addresses stack buffer overflow conditions, and CWE-122, which covers heap buffer overflow conditions. The memory corruption occurs at the kernel level through improper memory deallocation functions, specifically the dma_free_coherent() call with incorrect size parameters. The issue follows patterns consistent with ATT&CK technique T1059.003, which involves command and scripting interpreter usage, particularly in kernel space where memory management commands are misexecuted. The vulnerability also aligns with ATT&CK technique T1547.001, involving registry run keys and startup items, as it affects system-level resume operations that are critical for proper system state management.
Mitigation strategies for this vulnerability should focus on implementing proper memory tracking during the firmware communication process, ensuring that memory segment sizes are accurately maintained throughout the driver lifecycle. The fix involves modifying the ath12k driver to correctly handle memory segment accounting during resume operations, particularly by ensuring that the size parameters passed to dma_free_coherent() match the actual allocation sizes. System administrators should ensure that kernel updates containing the patched version are applied immediately, as this vulnerability can be exploited to cause denial of service conditions. Additionally, hardware configurations that support DMA remapping should be prioritized to avoid triggering this specific code path. Organizations should implement monitoring for kernel crash reports related to ath12k driver operations, particularly during system resume events, to detect potential exploitation attempts. The vulnerability underscores the importance of maintaining proper state consistency in kernel drivers during complex lifecycle operations such as suspend/resume cycles, where memory management decisions must be carefully tracked across different execution contexts.