CVE-2017-15843 in Android
Summary
by MITRE
Due to a race condition in a bus driver, a double free in msm_bus_floor_vote_context() can potentially occur in all Android releases from CAF (Android for MSM, Firefox OS for MSM, QRD Android) using the Linux Kernel.
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Analysis
by VulDB Data Team • 02/18/2020
The vulnerability identified as CVE-2017-15843 represents a critical race condition flaw within the msm_bus_floor_vote_context() function of the Linux kernel's bus driver implementation. This issue affects multiple Android variants including CAF Android, Firefox OS for MSM, and QRD Android, making it a widespread concern across Qualcomm-based mobile platforms. The vulnerability stems from improper synchronization mechanisms that fail to prevent concurrent access to shared resources during critical operations. The race condition specifically manifests when multiple threads attempt to manipulate the same memory context simultaneously, creating opportunities for memory corruption and system instability. This flaw exists in all Android releases that utilize the Linux kernel's msm bus driver framework, indicating a fundamental design issue rather than a simple coding error. The vulnerability's impact extends beyond individual device security to potentially compromise entire device fleets using affected Qualcomm chipsets.
The technical implementation of this vulnerability involves a double free condition that occurs when the msm_bus_floor_vote_context() function fails to properly validate or synchronize access to memory allocation structures. When multiple concurrent processes or threads attempt to vote for bus bandwidth or manipulate context structures, the lack of proper mutex locking or atomic operations allows for the same memory block to be freed twice. This race condition typically occurs during the process of allocating or deallocating bus vote contexts, where the kernel's memory management subsystem does not adequately protect against simultaneous access patterns. The flaw demonstrates poor adherence to memory safety principles and highlights the importance of proper synchronization in kernel-level code. According to CWE standards, this vulnerability maps to CWE-362, which specifically addresses race conditions in concurrent programming environments. The double free condition creates opportunities for memory corruption that could potentially be exploited to execute arbitrary code within kernel space.
The operational impact of CVE-2017-15843 extends beyond simple system crashes or instability, as it represents a potential entry point for privilege escalation attacks. When a double free occurs in kernel space, attackers can potentially manipulate memory layout to achieve code execution privileges, making this vulnerability particularly dangerous for mobile devices. The widespread nature of affected Android variants means that numerous devices across different manufacturers could be compromised, including smartphones, tablets, and other mobile computing platforms. This vulnerability directly impacts the integrity of the Android security model by creating potential pathways for malicious actors to gain elevated privileges within the device's operating system. The attack surface is particularly concerning given that these vulnerabilities affect not just consumer devices but also enterprise and industrial mobile platforms that rely on Qualcomm's msm bus driver implementations. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving privilege escalation and kernel exploitation, potentially enabling adversaries to establish persistent access to affected devices.
Mitigation strategies for CVE-2017-15843 should focus on immediate kernel updates and patches provided by device manufacturers, as well as implementing proper synchronization mechanisms within the affected driver code. Organizations should prioritize patch management programs to ensure all affected devices receive timely security updates from their respective manufacturers. The fix typically involves implementing proper mutex locking or atomic operations around the vulnerable code sections to prevent concurrent access to the bus vote context structures. System administrators should monitor for security advisories from Qualcomm and Android security teams, as these updates often include comprehensive fixes for race condition vulnerabilities. Additionally, runtime monitoring solutions can help detect anomalous memory access patterns that might indicate exploitation attempts. Network administrators should implement device monitoring protocols to identify potentially compromised devices within enterprise environments. The vulnerability underscores the importance of rigorous code review processes for kernel-level drivers and highlights the necessity of comprehensive security testing before deploying mobile platform components. Organizations should also consider implementing device isolation measures for affected platforms until proper patches are deployed to prevent potential exploitation across their device fleets.