CVE-2019-19768 in Linux
Summary
by MITRE
In the Linux kernel 5.4.0-rc2, there is a use-after-free (read) in the __blk_add_trace function in kernel/trace/blktrace.c (which is used to fill out a blk_io_trace structure and place it in a per-cpu sub-buffer).
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/12/2024
The vulnerability identified as CVE-2019-19768 represents a critical use-after-free condition in the Linux kernel version 5.4.0-rc2 affecting the block tracing subsystem. This flaw exists within the __blk_add_trace function located in kernel/trace/blktrace.c, which serves as the core mechanism for collecting I/O trace data and storing it within per-cpu sub-buffers. The vulnerability manifests when the kernel attempts to read from memory that has already been freed, creating a dangerous scenario where subsequent memory operations may access corrupted data structures. The issue specifically impacts the blk_io_trace structure management, which is fundamental to the kernel's ability to track and analyze block I/O operations across storage devices.
The technical exploitation of this vulnerability stems from improper memory management within the block tracing infrastructure where a pointer to a blk_io_trace structure is freed while still being referenced or accessed by other kernel components. This use-after-free condition creates opportunities for attackers to manipulate kernel memory layout and potentially execute arbitrary code with kernel privileges. The per-cpu sub-buffer mechanism that handles trace data aggregation becomes compromised when memory deallocation occurs before all references to the freed structure are properly invalidated. This flaw falls under the Common Weakness Enumeration category CWE-416, specifically addressing the use of freed memory vulnerability pattern that has been consistently documented in kernel security assessments.
The operational impact of CVE-2019-19768 extends beyond simple system instability to potentially enable privilege escalation attacks within kernel contexts. When an attacker can trigger the specific sequence leading to the use-after-free condition, they may be able to corrupt kernel data structures or manipulate memory contents to achieve unauthorized system access. The vulnerability affects systems running the Linux kernel 5.4.0-rc2 and potentially other versions where similar memory management patterns exist, making it particularly concerning for enterprise environments and cloud infrastructure where kernel-level attacks can compromise entire server fleets. The attack surface includes any system utilizing block tracing functionality, which is prevalent in storage-intensive applications and server environments.
Mitigation strategies for this vulnerability should prioritize immediate kernel updates to versions that have patched the memory management issue within the blktrace subsystem. System administrators should monitor for kernel security advisories and apply patches as soon as they become available, as the vulnerability can be exploited to gain root privileges on affected systems. Additional protective measures include implementing kernel lockdown mechanisms, restricting access to block tracing interfaces, and monitoring for anomalous I/O trace patterns that might indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1068, which addresses exploit for privilege escalation, while the technique of kernel memory corruption represents a sophisticated attack vector requiring careful system monitoring and robust patch management protocols. Organizations should also consider implementing kernel module integrity checks and runtime protection mechanisms to detect and prevent exploitation attempts targeting such fundamental kernel subsystems.