CVE-2016-3070 in Linux
Summary
by MITRE
The trace_writeback_dirty_page implementation in include/trace/events/writeback.h in the Linux kernel before 4.4 improperly interacts with mm/migrate.c, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact by triggering a certain page move.
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Analysis
by VulDB Data Team • 09/12/2022
The vulnerability identified as CVE-2016-3070 represents a critical flaw in the Linux kernel's writeback tracing mechanism that affects versions prior to 4.4. This issue resides within the trace_writeback_dirty_page implementation located in include/trace/events/writeback.h, where improper interaction with memory management components in mm/migrate.c creates a dangerous condition that can be exploited by local attackers. The flaw manifests when specific page migration operations occur during writeback processes, leading to a cascade of system instability that can result in complete system crashes or denial of service conditions.
The technical root cause of this vulnerability stems from a NULL pointer dereference that occurs during the page migration process when the kernel attempts to trace dirty page writeback operations. When memory pages are moved or migrated, the tracing subsystem fails to properly validate pointers that should reference page structures, resulting in a kernel panic when attempting to access null memory locations. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions in software systems. The interaction between the tracing subsystem and the memory migration code creates a scenario where the kernel's internal state becomes corrupted during page movement operations, particularly when dealing with dirty pages that require writeback processing.
The operational impact of this vulnerability extends beyond simple denial of service to potentially compromise system stability and availability. Local users with minimal privileges can trigger this condition by initiating page migration operations that cause the kernel to attempt to trace writeback activities on pages that have been moved or relocated. The system crash occurs when the tracing mechanism encounters a NULL reference while trying to access page metadata during the writeback process, leading to an immediate kernel panic and system reboot. This vulnerability can be particularly dangerous in production environments where system uptime is critical, as it allows any local user to potentially disrupt services or cause unexpected system interruptions.
From an attack perspective, this vulnerability aligns with ATT&CK technique T1068 which involves local privilege escalation and system compromise through kernel-level vulnerabilities. The exploitability of CVE-2016-3070 is enhanced by the fact that it requires no special privileges beyond local user access, making it a significant threat in multi-user environments. The vulnerability demonstrates the complexity of kernel-level interactions where seemingly independent subsystems can create dangerous dependencies that result in system-wide failures. Security practitioners should note that this vulnerability represents a classic example of how tracing and debugging mechanisms can introduce security risks when not properly integrated with core system operations.
Mitigation strategies for this vulnerability primarily focus on kernel version updates to 4.4 or later, where the interaction between trace_writeback_dirty_page and mm/migrate.c has been properly resolved. System administrators should prioritize patching affected systems and monitoring for any signs of exploitation attempts. Additionally, implementing proper access controls and limiting local user privileges can reduce the attack surface for this vulnerability. The fix implemented in kernel version 4.4 addresses the core pointer validation issue by ensuring that the tracing subsystem properly handles page migration scenarios and validates all pointers before dereferencing them during writeback operations. Organizations should also consider implementing kernel hardening measures and monitoring for anomalous page migration activities that might indicate exploitation attempts.