CVE-2017-11019 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, the fd allocated during the get_metadata was not closed even though the buffer allocated to the fd was freed. This resulted in a failure during exit sequence.
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Analysis
by VulDB Data Team • 12/21/2019
This vulnerability exists within the Linux kernel implementation used across various Android platforms including MSM variants, Firefox OS for MSM, and QRD Android systems. The flaw manifests during the metadata retrieval process where file descriptors are improperly managed, creating a resource leak condition that can escalate to system instability. The vulnerability specifically affects Android releases from CAF (Code Aurora Forum) that utilize the Linux kernel, making it widespread across numerous mobile devices and embedded systems. The issue stems from inadequate cleanup procedures during the exit sequence of kernel operations, where allocated file descriptors remain open despite the associated buffer memory being freed.
The technical root cause involves improper resource management within the kernel's metadata handling subsystem where the get_metadata function fails to properly close file descriptors that were allocated during its execution. When the function allocates memory for a buffer and subsequently frees it, the corresponding file descriptor remains open in the system's file descriptor table. This creates a situation where system resources become permanently tied up, leading to potential exhaustion of available file descriptors and ultimately causing the system to fail during normal exit sequences. The flaw represents a classic resource leak pattern that can be exploited to degrade system performance or cause complete system failure.
The operational impact of this vulnerability extends beyond simple resource consumption issues to potentially compromise system stability and availability. In mobile environments, this could result in application crashes, system hangs, or complete device reboot cycles during normal operation. The vulnerability is particularly concerning in embedded systems and automotive applications where system reliability is critical. Attackers could potentially exploit this weakness to cause denial of service conditions by repeatedly triggering the vulnerable code path, leading to progressive resource exhaustion. The issue also aligns with CWE-404, which specifically addresses improper resource management where allocated resources are not properly released, and can be mapped to ATT&CK technique T1499.004 for resource exhaustion attacks.
Mitigation strategies should focus on implementing proper resource cleanup procedures within the kernel code, ensuring that all file descriptors allocated during metadata operations are properly closed regardless of execution path. System administrators should apply the latest security patches from device manufacturers and kernel maintainers that address this specific resource leak condition. Additionally, monitoring systems should be implemented to detect abnormal file descriptor usage patterns that could indicate exploitation attempts. The fix typically involves modifying the get_metadata function to include explicit file descriptor closing operations in all code paths, including error handling scenarios, to ensure proper resource deallocation. Organizations should also consider implementing automated testing procedures that verify proper resource cleanup during kernel operations to prevent similar issues from emerging in future code releases.