CVE-2017-11091 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, in the function mdss_rotator_ioctl in the driver /dev/mdss_rotator, a Use-After-Free condition can potentially occur due to a fence being installed too early.
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Analysis
by VulDB Data Team • 12/07/2019
The vulnerability identified as CVE-2017-11091 represents a critical use-after-free condition within the Android kernel's multimedia driver subsystem, specifically affecting devices utilizing the Qualcomm Snapdragon chipset family. This flaw exists in the mdss_rotator_ioctl function located in the /dev/mdss_rotator driver interface, which manages rotation operations for display subsystem components. The issue stems from improper synchronization mechanisms within the kernel driver where a fence operation is executed prematurely, creating a window of opportunity for memory corruption vulnerabilities. The affected platforms include various Android releases from Code Aurora Forum (CAF) that utilize the Linux kernel, encompassing both standard Android implementations and Firefox OS variants targeting Qualcomm MSM (Multi-System Module) hardware platforms. This vulnerability impacts the fundamental graphics processing capabilities of mobile devices, particularly those utilizing Qualcomm's Mobile Display Subsystem (MDSS) architecture.
The technical exploitation of this vulnerability occurs through a race condition in the driver's ioctl (input/output control) interface handling, where the mdss_rotator_ioctl function processes rotation requests for display buffers. When a fence operation is installed before the completion of previous operations, it creates a scenario where freed memory locations may still be referenced by subsequent operations. This premature fence installation allows malicious actors to potentially manipulate the driver's memory management state, leading to arbitrary code execution privileges. The underlying cause aligns with CWE-416, which describes use-after-free vulnerabilities where memory is accessed after it has been freed, and the timing aspect relates to CWE-362, representing a race condition that enables concurrent access to shared resources. The vulnerability's exploitation typically requires kernel-level privileges or a method to execute code within the kernel context, making it particularly dangerous as it could enable full system compromise.
The operational impact of CVE-2017-11091 extends beyond simple memory corruption, potentially allowing attackers to gain unauthorized access to critical system resources and execute malicious code with kernel privileges. This vulnerability affects devices that utilize Qualcomm's MDSS display subsystem, which is prevalent across numerous smartphone and tablet models from various manufacturers including Samsung, LG, Motorola, and others that incorporate Snapdragon processors. The exploitation of this vulnerability could result in complete system compromise, enabling attackers to bypass security restrictions, access sensitive user data, modify system files, or establish persistent backdoors. Additionally, since this affects multiple Android versions and firmware implementations, the attack surface is extensive, potentially impacting millions of devices globally. The vulnerability's classification under the ATT&CK framework would fall under privilege escalation techniques, specifically targeting kernel-level access through driver exploitation, with potential for lateral movement once the initial compromise is achieved.
Mitigation strategies for CVE-2017-11091 primarily involve applying the vendor-provided security patches and kernel updates from Code Aurora Forum and device manufacturers. Organizations and users should prioritize immediate deployment of the patched kernel versions that address the premature fence installation issue in the mdss_rotator driver. System administrators should implement comprehensive patch management protocols to ensure all affected devices receive timely updates, particularly focusing on enterprise devices that may have extended support cycles. Additional defensive measures include monitoring for anomalous kernel behavior, implementing kernel module integrity checks, and establishing robust device monitoring systems to detect potential exploitation attempts. The vulnerability highlights the importance of proper synchronization mechanisms in kernel drivers and reinforces the need for thorough security testing of device drivers, particularly those handling graphics and display operations. Security teams should also consider implementing runtime protection mechanisms and memory corruption detection systems to identify and prevent exploitation attempts targeting similar race condition vulnerabilities in other kernel subsystems.