CVE-2011-2909 in Linux
Summary
by MITRE
The do_devinfo_ioctl function in drivers/staging/comedi/comedi_fops.c in the Linux kernel before 3.1 allows local users to obtain sensitive information from kernel memory via a copy of a short string.
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Analysis
by VulDB Data Team • 03/11/2022
The vulnerability identified as CVE-2011-2909 resides within the Linux kernel's staging comedi driver subsystem, specifically in the do_devinfo_ioctl function located in drivers/staging/comedi/comedi_fops.c. This flaw represents a classic information disclosure vulnerability that affects kernel versions prior to 3.1, creating a significant security risk for systems utilizing the comedi framework for data acquisition and control applications. The comedi driver is designed to support various data acquisition hardware devices including analog and digital input/output boards, making it a critical component in industrial automation and scientific instrumentation environments.
The technical implementation of this vulnerability stems from improper bounds checking within the ioctl handling mechanism of the comedi driver. When a user-space application invokes the do_devinfo_ioctl function through a device file interface, the kernel function fails to properly validate the length of string data being copied from user space to kernel space. This insufficient validation allows local users to craft malicious ioctl requests that can cause the kernel to copy kernel memory contents to user space, potentially exposing sensitive data including kernel addresses, configuration information, and other confidential system data. The vulnerability specifically manifests when handling short string operations, where the function does not adequately verify that the buffer size specified by the user matches the actual data being copied.
The operational impact of this vulnerability extends beyond simple information disclosure, as the leaked kernel memory can contain critical system information that could aid attackers in developing more sophisticated exploits. Local users with access to the system can leverage this vulnerability to gather kernel addresses, which can be used for bypassing kernel address space layout randomization defenses and other exploit mitigation techniques. The exposure of kernel memory contents also reveals information about the system's internal state, including potentially sensitive configuration parameters and data structures that could be valuable for privilege escalation or targeted attacks. This vulnerability particularly affects systems running older kernel versions where the comedi subsystem is actively used for hardware control and data acquisition tasks.
Mitigation strategies for CVE-2011-2909 primarily involve upgrading to Linux kernel version 3.1 or later, where the vulnerability has been addressed through proper bounds checking implementation in the ioctl handling function. System administrators should also implement the principle of least privilege by restricting access to comedi device files to only authorized users and processes, thereby limiting the attack surface. Additionally, monitoring for unusual ioctl activity patterns and implementing kernel hardening measures such as stack canaries and kernel address space layout randomization can help detect and prevent exploitation attempts. This vulnerability aligns with CWE-200, which categorizes information disclosure flaws, and represents a typical example of how insufficient input validation in kernel space can lead to critical security consequences. The ATT&CK framework would classify this as a privilege escalation technique through kernel memory exposure, potentially enabling further malicious activities within the compromised system environment.