CVE-2021-47022 in Linux
Summary
by MITRE • 02/28/2024
In the Linux kernel, the following vulnerability has been resolved:
mt76: mt7615: fix memleak when mt7615_unregister_device()
mt7615_tx_token_put() should get call before mt76_free_pending_txwi().
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Analysis
by VulDB Data Team • 12/09/2024
The vulnerability identified as CVE-2021-47022 represents a memory leak in the Linux kernel's mt76 wireless driver subsystem, specifically affecting the mt7615 device implementation. This issue resides within the wireless networking stack where improper resource management leads to memory allocation that is never properly released, creating a persistent memory leak condition that can degrade system performance over time. The flaw manifests during the device unregistering process when the driver attempts to clean up allocated resources.
The technical root cause stems from an incorrect order of function calls within the device cleanup routine. Specifically, the mt7615_tx_token_put() function which is responsible for releasing transmit tokens must be invoked before mt76_free_pending_txwi() which handles freeing pending transmit work items. This ordering dependency is critical because transmit tokens represent a specific type of kernel memory resource that must be properly returned to their respective pools before the associated work items can be safely freed. When this sequence is violated, the transmit tokens remain allocated in memory pools, preventing their reuse and causing progressive memory consumption.
The operational impact of this memory leak extends beyond simple resource waste, potentially leading to system instability and performance degradation in wireless networking environments. As the leak accumulates over time, it can contribute to memory pressure that affects other kernel subsystems and applications. The vulnerability is particularly concerning in embedded systems or devices with limited memory resources where such leaks can quickly lead to system crashes or complete loss of wireless connectivity. Network administrators monitoring systems running affected kernel versions may observe gradual memory consumption increases that correlate with wireless activity.
This vulnerability aligns with CWE-401, which addresses improper handling of memory allocation and deallocation, specifically focusing on memory leaks in kernel space. The issue also relates to ATT&CK technique T1059.007 which covers command and scripting interpreter usage, as memory leaks in kernel drivers can indirectly affect system stability and potentially provide attack vectors for resource exhaustion attacks. The proper fix involves enforcing the correct sequence of function calls within the mt7615_unregister_device() routine to ensure that all transmit tokens are properly returned before pending work items are freed. System administrators should upgrade to kernel versions containing the patched mt76 driver implementation to mitigate this vulnerability and prevent potential memory exhaustion scenarios that could impact wireless networking reliability.