CVE-2017-9705 in Android
Summary
by MITRE
In Android for MSM, Firefox OS for MSM, QRD Android, with all Android releases from CAF using the Linux kernel, concurrent rx notifications and read() operations in the G-Link PKT driver can result in a double free condition due to missing locking resulting in list_del() and list_add() overlapping and corrupting the next and previous pointers.
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Analysis
by VulDB Data Team • 01/29/2021
The vulnerability identified as CVE-2017-9705 represents a critical memory corruption issue within the G-Link PKT driver component of Android-based systems. This flaw affects multiple Android releases from Code Aurora Forum (CAF) that utilize the Linux kernel, including MSM (Mobile Station Modem) variants and Firefox OS for MSM platforms. The vulnerability stems from insufficient synchronization mechanisms within the driver's implementation, creating a race condition scenario that can lead to severe system instability and potential privilege escalation.
The technical root cause of this vulnerability lies in the missing locking mechanisms within the G-Link PKT driver's handling of concurrent read operations and receive notifications. When multiple threads attempt to access the driver simultaneously, the absence of proper mutex or spinlock protection allows for overlapping execution paths during list manipulation operations. Specifically, the driver performs list_del() and list_add() operations on linked lists without adequate synchronization, creating a scenario where two or more threads can simultaneously modify the same list structure. This concurrent access pattern results in a double free condition where memory allocated to list nodes gets freed twice, causing corruption of the next and previous pointers that maintain the integrity of the linked list structure.
The operational impact of this vulnerability extends beyond simple system crashes, as it creates potential attack vectors for privilege escalation and system compromise. An attacker who can trigger the race condition through controlled concurrent access to the G-Link PKT driver could potentially execute arbitrary code with kernel-level privileges. The double free condition corrupts the kernel's memory management structures, which can lead to unpredictable behavior including system hangs, kernel panics, or more critically, the ability to manipulate kernel data structures to gain unauthorized access to system resources. This vulnerability particularly affects mobile devices where the G-Link PKT driver handles communication between different system components and external hardware.
The vulnerability aligns with CWE-367, which describes Time-of-Check to Time-of-Use (TOCTOU) race conditions, and represents a classic example of improper locking in kernel space drivers. From an ATT&CK perspective, this weakness maps to privilege escalation techniques and kernel exploitation methods, as the vulnerability allows for bypassing kernel memory protection mechanisms. The flaw demonstrates the critical importance of proper synchronization in kernel drivers, as highlighted in the NSA's Cybersecurity Technical Report on kernel security vulnerabilities. Mitigation strategies should include implementing proper locking mechanisms using mutexes or spinlocks to prevent concurrent access to shared data structures, updating to patched versions of the affected Android releases, and applying kernel security patches that address the specific race condition in the G-Link PKT driver implementation. Organizations should also conduct thorough security assessments of their mobile device fleets to identify systems running vulnerable versions of the affected software components and implement timely remediation measures to prevent exploitation.