CVE-2019-19064 in Linux
Summary
by MITRE
A memory leak in the fsl_lpspi_probe() function in drivers/spi/spi-fsl-lpspi.c in the Linux kernel through 5.3.11 allows attackers to cause a denial of service (memory consumption) by triggering pm_runtime_get_sync() failures, aka CID-057b8945f78f.
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Analysis
by VulDB Data Team • 08/05/2024
The vulnerability identified as CVE-2019-19064 represents a critical memory management flaw within the Linux kernel's Freescale Low Power SPI driver implementation. This issue manifests in the fsl_lpspi_probe() function located in drivers/spi/spi-fsl-lpspi.c, affecting kernel versions through 5.3.11. The vulnerability operates through a memory leak mechanism that occurs when the pm_runtime_get_sync() function fails during device initialization, creating a condition where allocated memory resources are not properly released back to the system. This failure path represents a fundamental breakdown in resource management practices within the kernel's device driver framework, specifically impacting SPI bus controllers that utilize the Freescale Low Power SPI interface.
The technical exploitation of this vulnerability occurs when an attacker can trigger conditions that cause pm_runtime_get_sync() to return an error status during the probe phase of SPI device initialization. When this failure occurs, the memory allocation that would normally be cleaned up in the successful code path is not properly deallocated, leading to gradual memory consumption over time. The root cause stems from improper error handling within the driver's probe function where memory is allocated for device structures and runtime power management resources, but the cleanup routine is bypassed when the pm_runtime_get_sync() call fails. This pattern aligns with CWE-401: Improper Release of Memory and represents a classic case of resource leak that can be systematically exploited to cause system instability.
The operational impact of this vulnerability extends beyond simple memory consumption, creating potential denial of service conditions that can severely impact system stability and availability. When multiple SPI devices are present or when the vulnerable driver is repeatedly probed under error conditions, the memory leak compounds, potentially leading to system memory exhaustion and subsequent kernel oops or system crashes. The vulnerability affects systems running Linux kernel versions up to 5.3.11, making it particularly concerning for embedded systems and IoT devices that often utilize Freescale SPI controllers and may not receive timely kernel updates. The attack vector is relatively straightforward, requiring only the ability to trigger device probe operations or induce runtime power management failures, making this vulnerability particularly dangerous in environments where device hot-plugging or error conditions are common.
Mitigation strategies for CVE-2019-19064 should focus on immediate kernel version upgrades to 5.3.12 or later, where the memory leak has been addressed through proper error handling and resource cleanup mechanisms. System administrators should implement monitoring solutions to detect unusual memory consumption patterns that may indicate exploitation attempts, particularly in systems with multiple SPI devices or high-frequency device probing. The fix implemented in the patched kernel versions involves ensuring that all allocated memory structures are properly freed even when pm_runtime_get_sync() fails, implementing proper cleanup routines in error paths, and maintaining consistent resource management practices throughout the driver's probe and remove functions. This vulnerability demonstrates the importance of comprehensive error handling in kernel drivers and aligns with ATT&CK technique T1499.004: Endpoint Denial of Service, where memory exhaustion attacks can be leveraged to create system instability and service unavailability. Organizations should also consider implementing device-specific runtime power management policies and monitoring for unusual device probe patterns as part of their overall security posture to prevent exploitation of similar resource leak vulnerabilities in other kernel subsystems.