CVE-2019-15922 in Linux
Summary
by MITRE
An issue was discovered in the Linux kernel before 5.0.9. There is a NULL pointer dereference for a pf data structure if alloc_disk fails in drivers/block/paride/pf.c.
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Analysis
by VulDB Data Team • 12/13/2023
The vulnerability identified as CVE-2019-15922 represents a critical NULL pointer dereference flaw within the Linux kernel's paride subsystem, specifically affecting versions prior to 5.0.9. This issue resides in the drivers/block/paride/pf.c file where the kernel fails to properly handle memory allocation failures during disk structure initialization. The paride subsystem is responsible for managing parallel port IDE devices, including various storage peripherals that communicate through the parallel interface. When the alloc_disk function encounters a failure during memory allocation for disk data structures, the kernel does not adequately check for this condition before proceeding with operations that assume the allocation succeeded, leading to a NULL pointer dereference.
The technical implementation of this vulnerability stems from inadequate error handling within the kernel's device initialization code. When alloc_disk fails to allocate memory for a disk structure, it returns a NULL pointer to the calling function. However, subsequent code in the pf.c driver does not validate this return value before attempting to access members of the NULL data structure. This pattern violates fundamental kernel programming practices and represents a classic example of improper error handling that can lead to system crashes or potential privilege escalation. The flaw operates at the kernel level where memory management and device initialization occur, making it particularly dangerous as it can affect system stability and potentially provide attackers with opportunities to exploit the kernel's memory management subsystem.
The operational impact of CVE-2019-15922 extends beyond simple system crashes, as it can be leveraged in various attack scenarios. The NULL pointer dereference can cause immediate system panics or kernel oops, resulting in denial of service conditions that may be exploited by malicious actors to disrupt system availability. In environments where parallel port devices are actively used, this vulnerability could be triggered through normal device enumeration processes, making it particularly concerning for embedded systems, servers, and desktop environments running affected kernel versions. The vulnerability aligns with CWE-476 which specifically addresses NULL pointer dereference issues in software systems, and could potentially map to ATT&CK technique T1068 which involves local privilege escalation through kernel exploits. The flaw demonstrates how seemingly minor error handling oversights in kernel code can result in significant security implications.
Mitigation strategies for CVE-2019-15922 primarily focus on upgrading to kernel versions 5.0.9 or later where the issue has been resolved through proper error checking implementation. System administrators should prioritize patching affected systems, particularly those running older kernel versions or custom kernels that may not have received the specific fix. The patch for this vulnerability typically involves adding explicit NULL pointer checks after alloc_disk calls, ensuring that the kernel properly validates memory allocation success before proceeding with operations on the allocated data structures. Organizations should also implement monitoring for kernel oops messages or system crashes that may indicate exploitation attempts. Additional defensive measures include restricting access to parallel port devices where possible and implementing proper kernel hardening configurations that limit potential attack surface areas. The fix demonstrates the importance of robust error handling in kernel space code and serves as a reminder of how critical proper resource management is in maintaining system stability and security.