CVE-2016-10154 in Linux
Summary
by MITRE
The smbhash function in fs/cifs/smbencrypt.c in the Linux kernel 4.9.x before 4.9.1 interacts incorrectly with the CONFIG_VMAP_STACK option, which allows local users to cause a denial of service (system crash or memory corruption) or possibly have unspecified other impact by leveraging use of more than one virtual page for a scatterlist.
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Analysis
by VulDB Data Team • 11/11/2022
The vulnerability identified as CVE-2016-10154 resides within the Linux kernel's CIFS (Common Internet File System) implementation, specifically in the smbhash function located in fs/cifs/smbencrypt.c. This flaw manifests in kernel versions 4.9.x prior to 4.9.1 and represents a critical issue that affects systems utilizing the CONFIG_VMAP_STACK configuration option. The vulnerability stems from an improper interaction between the smbhash function and virtual memory management when handling scatterlist operations that require multiple virtual pages. When the system processes CIFS network operations involving authentication or data transfer, the kernel's handling of virtual memory pages becomes inconsistent, creating a pathway for exploitation that can result in system instability.
The technical root cause of this vulnerability lies in how the smbhash function manages memory allocation and page handling when the CONFIG_VMAP_STACK option is enabled. This configuration option allows the kernel to use virtual memory mapping for stack allocation, which can span multiple virtual pages. During CIFS operations, particularly those involving authentication hashes, the function fails to properly account for the virtual memory layout when processing scatterlists that extend beyond a single page boundary. This mismanagement creates a scenario where memory corruption can occur during the hash computation process, leading to either system crashes or more subtle memory corruption that could potentially be exploited for privilege escalation or other malicious activities.
The operational impact of this vulnerability extends beyond simple denial of service conditions, as it represents a potential vector for more serious security compromises. Local attackers with access to the system can trigger the vulnerability by initiating CIFS operations that utilize the affected code path, potentially causing system crashes that disrupt legitimate services. However, the more concerning aspect involves the potential for memory corruption that could allow attackers to manipulate kernel memory structures, possibly leading to privilege escalation or the execution of arbitrary code within kernel space. The vulnerability's exploitation requires local system access but does not necessitate network connectivity, making it particularly dangerous in environments where local privilege escalation is a concern.
Mitigation strategies for CVE-2016-10154 primarily focus on updating to kernel versions 4.9.1 or later where the vulnerability has been patched. System administrators should prioritize kernel updates, particularly in production environments where the CONFIG_VMAP_STACK option is enabled. Additionally, organizations can consider disabling the CONFIG_VMAP_STACK option if it is not essential for their specific use cases, though this may impact system performance and memory management capabilities. Security monitoring should include detection of unusual system crashes or memory corruption patterns that could indicate exploitation attempts. The vulnerability aligns with CWE-121, which addresses stack-based buffer overflow conditions, and potentially with ATT&CK techniques involving privilege escalation and system compromise through kernel vulnerabilities. Organizations should also implement comprehensive patch management procedures to ensure timely deployment of security fixes and maintain visibility into kernel-level operations that could be affected by similar memory management issues.