CVE-2017-10911 in Linux
Summary
by MITRE
The make_response function in drivers/block/xen-blkback/blkback.c in the Linux kernel before 4.11.8 allows guest OS users to obtain sensitive information from host OS (or other guest OS) kernel memory by leveraging the copying of uninitialized padding fields in Xen block-interface response structures, aka XSA-216.
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Analysis
by VulDB Data Team • 12/09/2022
The vulnerability identified as CVE-2017-10911 represents a critical information disclosure flaw within the Linux kernel's Xen block backend driver implementation. This vulnerability specifically affects versions prior to kernel 4.11.8 and resides in the make_response function located within drivers/block/xen-blkback/blkback.c. The issue stems from improper handling of memory structures during the processing of block I/O operations between guest and host operating systems in virtualized environments. The flaw enables malicious guest OS users to extract sensitive kernel memory contents through exploitation of uninitialized padding fields within Xen block interface response structures.
The technical mechanism behind this vulnerability involves the copying of uninitialized memory regions during the construction of block response messages. When the make_response function processes I/O requests from guest operating systems, it creates response structures that contain padding fields which are not properly initialized before being copied to the guest. These padding fields may retain data from previous operations or kernel memory allocations, effectively leaking confidential information from the host kernel memory space. The vulnerability is particularly dangerous because it allows guest users to access memory that should remain isolated, potentially exposing kernel data structures, cryptographic keys, or other sensitive information that could be leveraged for further exploitation.
From an operational perspective, this vulnerability creates significant security risks in virtualized environments where multiple guest operating systems share the same host infrastructure. The information disclosure can be exploited to gain insights into the host kernel's memory layout, potentially enabling attackers to bypass security mechanisms such as kernel address space layout randomization or other memory protection features. The impact extends beyond simple information leakage as the leaked memory contents could contain sensitive data that aids in privilege escalation attacks or helps attackers develop more sophisticated exploitation techniques. This vulnerability particularly affects cloud computing environments and virtualization platforms where guest isolation is critical for maintaining security boundaries between different tenants.
The vulnerability maps to CWE-200, which describes "Information Exposure," and specifically relates to improper handling of uninitialized memory structures. From an attack framework perspective, this issue aligns with ATT&CK technique T1059.001 for command and scripting interpreter and T1068 for exploit for privilege escalation. The primary mitigation strategy involves upgrading to Linux kernel version 4.11.8 or later where the vulnerability has been patched. The fix implemented by the kernel maintainers ensures proper initialization of all padding fields within the response structures before copying them to guest memory. Additionally, system administrators should implement monitoring for unusual memory access patterns and consider implementing additional virtualization security controls such as kernel module signing and restricted guest access policies to minimize potential impact from similar vulnerabilities. Organizations running virtualized infrastructure should prioritize patching this vulnerability as it represents a fundamental breakdown in the isolation guarantees provided by hypervisor-based virtualization.