CVE-2017-18255 in Linux
Summary
by MITRE
The perf_cpu_time_max_percent_handler function in kernel/events/core.c in the Linux kernel before 4.11 allows local users to cause a denial of service (integer overflow) or possibly have unspecified other impact via a large value, as demonstrated by an incorrect sample-rate calculation.
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Analysis
by VulDB Data Team • 02/26/2023
The vulnerability identified as CVE-2017-18255 resides within the Linux kernel's performance monitoring subsystem, specifically in the perf_cpu_time_max_percent_handler function located in kernel/events/core.c. This flaw represents a critical integer overflow condition that affects Linux kernel versions prior to 4.11, creating a potential pathway for local privilege escalation and system instability. The vulnerability manifests when malicious users provide excessively large values to the performance monitoring interface, leading to miscalculations in sample rate computations that can result in system-wide denial of service conditions.
The technical implementation of this vulnerability stems from improper input validation within the performance monitoring framework's CPU time maximum percentage handler. When a large value is passed to the function, the integer overflow occurs during the calculation of sample rates, causing the system to miscalculate performance monitoring parameters. This flaw operates at the kernel level, making it particularly dangerous as it can be exploited by local users without requiring special privileges. The integer overflow specifically impacts the calculation logic that determines how frequently performance events are sampled, potentially causing the monitoring subsystem to behave erratically or crash entirely.
The operational impact of CVE-2017-18255 extends beyond simple denial of service scenarios, as the vulnerability could potentially enable more sophisticated attacks through unspecified other impacts. The integer overflow condition creates opportunities for memory corruption or unexpected behavior within the kernel's performance monitoring subsystem, which may be exploitable for privilege escalation or information disclosure. System administrators face significant risks when running vulnerable kernel versions, as local attackers can leverage this flaw to disrupt system operations or potentially gain elevated privileges. The vulnerability's classification aligns with CWE-191, which addresses integer underflow or overflow conditions, and maps to ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation' through kernel exploits.
Mitigation strategies for CVE-2017-18255 primarily focus on kernel version updates to 4.11 or later, where the integer overflow issue has been resolved through proper input validation and overflow protection mechanisms. System administrators should implement immediate patching procedures for all affected systems, particularly those running kernel versions between 2.6.32 and 4.10. Additional defensive measures include monitoring performance monitoring subsystem logs for unusual activity patterns and implementing proper access controls to limit local user privileges. The vulnerability demonstrates the importance of input validation in kernel space code and highlights how seemingly benign parameter handling can create critical security flaws. Organizations should also consider implementing kernel lockdown mechanisms and restricting local user access to performance monitoring interfaces where possible. The resolution of this vulnerability through kernel updates reflects the ongoing need for rigorous code review processes in kernel development, particularly for functions handling user-provided parameters in security-critical subsystems.