CVE-2014-9940 in Linux
Summary
by MITRE
The regulator_ena_gpio_free function in drivers/regulator/core.c in the Linux kernel before 3.19 allows local users to gain privileges or cause a denial of service (use-after-free) via a crafted application.
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Analysis
by VulDB Data Team • 12/06/2022
The vulnerability identified as CVE-2014-9940 represents a critical use-after-free flaw within the Linux kernel's regulator subsystem, specifically affecting the regulator_ena_gpio_free function located in drivers/regulator/core.c. This issue exists in kernel versions prior to 3.19 and creates a significant security risk by allowing local attackers to exploit a memory management error that can lead to privilege escalation or system instability. The vulnerability stems from improper handling of GPIO (General Purpose Input/Output) resources within the power management framework, where the kernel fails to properly validate or manage the lifecycle of regulator enable GPIO resources, creating opportunities for malicious code execution.
The technical exploitation of this vulnerability occurs when a local user crafts a malicious application that triggers the regulator_ena_gpio_free function with improper resource handling. When the function attempts to free memory that has already been released or is in an invalid state, it creates a use-after-free condition that can be leveraged by attackers to execute arbitrary code with elevated privileges. This type of vulnerability falls under CWE-416, which specifically addresses the use of freed memory, and aligns with the ATT&CK technique T1068 which covers local privilege escalation through kernel vulnerabilities. The flaw exists because the kernel's regulator subsystem does not properly synchronize access to GPIO resources or validate the state of these resources before attempting to free them, creating a race condition that can be exploited by malicious applications.
The operational impact of CVE-2014-9940 extends beyond simple privilege escalation to encompass potential system compromise and denial of service scenarios. Local users who can execute arbitrary code on a vulnerable system can leverage this vulnerability to gain root privileges, effectively taking complete control over the device or server. This is particularly concerning in embedded systems, mobile devices, and server environments where kernel-level access can provide attackers with unrestricted system control. The vulnerability affects systems running Linux kernel versions 3.18 and earlier, making it relevant to a substantial portion of deployed systems that had not yet received the security patch. The use-after-free condition can also lead to system crashes or hangs, creating a denial of service scenario that could be exploited by attackers seeking to disrupt system availability.
Mitigation strategies for this vulnerability primarily involve applying the appropriate kernel security patches released by the Linux kernel development team, specifically upgrading to kernel version 3.19 or later where the vulnerability has been addressed. System administrators should prioritize patch management and ensure all production systems receive the necessary updates to prevent exploitation. Additional protective measures include implementing strict access controls to limit local user privileges, monitoring for suspicious system behavior that might indicate exploitation attempts, and employing kernel security modules such as grsecurity or PaX that provide additional protection against memory corruption vulnerabilities. The fix implemented by the kernel developers typically involves proper resource validation and synchronization mechanisms that prevent the premature freeing of GPIO resources, ensuring that memory management operations occur only when resources are in a valid state and properly synchronized across all access paths. Organizations should also conduct vulnerability assessments to identify systems running affected kernel versions and implement comprehensive monitoring to detect potential exploitation attempts that might leverage this or similar use-after-free conditions.