CVE-2017-8247 in Android
Summary
by MITRE
In all Qualcomm products with Android releases from CAF using the Linux kernel, if there is more than one thread doing the device open operation, the device may be opened more than once. This would lead to get_pid being called more than once, however put_pid being called only once in function "msm_close".
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Analysis
by VulDB Data Team • 01/13/2021
The vulnerability described in CVE-2017-8247 represents a critical resource management flaw affecting Qualcomm products that utilize Android-based systems with Linux kernel implementations. This issue stems from improper handling of device file operations within the multimedia subsystem, specifically impacting how the kernel manages process identifiers during concurrent access scenarios. The flaw manifests when multiple threads attempt to open the same device simultaneously, creating a scenario where the kernel's reference counting mechanism becomes inconsistent, leading to potential system instability and security implications.
The technical root cause of this vulnerability lies in the msm_close function within the Linux kernel's multimedia subsystem implementation. When multiple threads access a device file concurrently, the get_pid function is invoked multiple times to acquire process identifiers for each thread, but the corresponding put_pid function is only called once during the close operation. This mismatch creates a reference counting discrepancy that can result in improper resource deallocation and potential memory corruption. The vulnerability is classified as a resource leak and improper cleanup issue that directly impacts the kernel's ability to properly manage process references, making it susceptible to exploitation through race conditions and concurrent access patterns.
The operational impact of this vulnerability extends beyond simple resource leakage to potentially enable more serious security exploits. When process identifiers are not properly released, the system may experience memory exhaustion or corrupted process state information that could be leveraged by malicious actors. This type of vulnerability is particularly concerning in mobile environments where multiple applications and system services frequently access multimedia devices concurrently. The flaw can lead to system crashes, denial of service conditions, or potentially provide attackers with opportunities to escalate privileges through improper resource handling. According to CWE classification, this vulnerability maps to CWE-410: Insufficient Resource Management and CWE-755: Improper Handling of Exceptional Conditions, highlighting the fundamental issues with resource allocation and cleanup.
Mitigation strategies for CVE-2017-8247 should focus on implementing proper reference counting mechanisms within the kernel's device management code. System administrators and developers should ensure that all device close operations properly account for all active references and call corresponding cleanup functions for each acquired resource. The fix typically involves modifying the msm_close function to properly track and release all process identifiers acquired during the device open sequence, ensuring that put_pid is called once for each get_pid invocation. Additionally, implementing proper locking mechanisms and synchronization primitives can prevent race conditions that lead to this vulnerability. Organizations should also consider applying the relevant kernel patches provided by Qualcomm and the Android Open Source Project, as these updates contain the necessary code modifications to address the reference counting inconsistency. From an ATT&CK perspective, this vulnerability could be exploited as part of privilege escalation techniques, specifically through the use of resource exhaustion or memory corruption methods that leverage improper reference counting behavior.