CVE-2022-33981 in Linux
Summary
by MITRE • 06/18/2022
drivers/block/floppy.c in the Linux kernel before 5.17.6 is vulnerable to a denial of service, because of a concurrency use-after-free flaw after deallocating raw_cmd in the raw_cmd_ioctl function.
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Analysis
by VulDB Data Team • 06/19/2022
The vulnerability identified as CVE-2022-33981 represents a critical concurrency issue within the Linux kernel's floppy disk driver implementation. This flaw exists in the drivers/block/floppy.c file and affects kernel versions prior to 5.17.6, creating a significant risk for systems relying on floppy disk functionality or those that might inadvertently trigger the vulnerable code path. The issue stems from improper handling of memory management within a multi-threaded context where race conditions can occur during device command processing.
The technical root cause of this vulnerability lies in a use-after-free condition that manifests when the raw_cmd structure is deallocated within the raw_cmd_ioctl function. When concurrent threads access the floppy device driver simultaneously, one thread may free the raw_cmd memory while another thread attempts to reference it, leading to undefined behavior and potential system instability. This type of flaw falls under the CWE-416 category of Use After Free, which is classified as a critical memory safety issue that can lead to arbitrary code execution or system crashes. The concurrency aspect makes this particularly dangerous as it can be triggered through normal device operation patterns rather than requiring specific malicious input.
The operational impact of this vulnerability extends beyond simple denial of service scenarios, as it can result in complete system crashes or unpredictable behavior in kernel space. When the use-after-free condition occurs, the kernel may experience memory corruption that leads to kernel oops, system panics, or more insidiously, allows for potential privilege escalation attacks. Attackers could potentially exploit this vulnerability by crafting specific ioctl commands that trigger the race condition, causing the system to become unresponsive or potentially allowing for more sophisticated attacks that leverage the memory corruption for privilege escalation. The vulnerability affects systems where floppy disk support is compiled into the kernel or where the device driver is dynamically loaded, making it a widespread concern across various Linux distributions.
Mitigation strategies for CVE-2022-33981 primarily involve upgrading to Linux kernel version 5.17.6 or later where the fix has been implemented. The fix addresses the race condition by properly synchronizing access to the raw_cmd structure and ensuring that memory deallocation occurs only after all references have been cleared. System administrators should also consider disabling floppy disk support entirely if the functionality is not required, which can be achieved through kernel configuration options or module blacklisting. Additionally, monitoring for unusual system behavior or kernel panic messages that might indicate exploitation attempts can provide early detection capabilities. The ATT&CK framework categorizes this type of vulnerability under T1059.003 for kernel-mode rootkits and T1499.004 for network denial of service, highlighting the potential for both system stability compromise and broader network impact. Organizations should implement comprehensive patch management processes to ensure timely deployment of kernel updates and consider conducting security assessments to identify systems running vulnerable kernel versions.