CVE-2017-9150 in Linux
Summary
by MITRE
The do_check function in kernel/bpf/verifier.c in the Linux kernel before 4.11.1 does not make the allow_ptr_leaks value available for restricting the output of the print_bpf_insn function, which allows local users to obtain sensitive address information via crafted bpf system calls.
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Analysis
by VulDB Data Team • 12/21/2024
The vulnerability identified as CVE-2017-9150 resides within the Linux kernel's eBPF (extended Berkeley Packet Filter) subsystem, specifically in the kernel/bpf/verifier.c file. This flaw affects Linux kernel versions prior to 4.11.1 and represents a significant information disclosure vulnerability that can be exploited by local attackers to gain sensitive address information. The vulnerability stems from a design oversight in how the BPF verifier handles pointer leak restrictions during kernel execution.
The technical flaw manifests in the do_check function where the allow_ptr_leaks value is not properly propagated to restrict the output of the print_bpf_insn function. This oversight creates a pathway for malicious code to extract kernel memory addresses through crafted bpf system calls. When the BPF verifier processes instructions, it fails to enforce proper pointer leak restrictions that should prevent sensitive address information from being exposed through debugging output mechanisms. The allow_ptr_leaks parameter, which should control whether pointer information can be leaked during verification, is not correctly utilized in the context of instruction printing operations.
The operational impact of this vulnerability is substantial for local attackers who can leverage it to perform kernel address space layout randomization (ASLR) bypass techniques. By exploiting this flaw, an attacker can obtain kernel memory addresses that would otherwise be protected by ASLR, significantly weakening the kernel's security posture. This information disclosure can be particularly dangerous when combined with other vulnerabilities, as it provides attackers with the precise memory locations needed to craft more sophisticated exploits. The vulnerability affects systems running vulnerable kernel versions and can be exploited by any local user with the ability to execute bpf system calls.
This vulnerability maps to CWE-200 (Information Exposure) and aligns with ATT&CK technique T1059.006 (Command and Scripting Interpreter: Python) and T1068 (Exploitation for Privilege Escalation) within the MITRE ATT&CK framework. The flaw demonstrates a classic case of insufficient input validation and output sanitization in kernel space operations. Organizations should prioritize patching affected systems to kernel version 4.11.1 or later, where the fix properly implements the allow_ptr_leaks restriction in the print_bpf_insn function. System administrators should also monitor for suspicious bpf system call usage and consider implementing additional security controls such as mandatory access controls or kernel module signing to further mitigate potential exploitation risks. The vulnerability highlights the critical importance of proper privilege separation and output sanitization in kernel subsystems, particularly those handling user-supplied code execution.