CVE-2017-7187 in Linux
Summary
by MITRE
The sg_ioctl function in drivers/scsi/sg.c in the Linux kernel through 4.10.4 allows local users to cause a denial of service (stack-based buffer overflow) or possibly have unspecified other impact via a large command size in an SG_NEXT_CMD_LEN ioctl call, leading to out-of-bounds write access in the sg_write function.
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Analysis
by VulDB Data Team • 11/14/2022
The vulnerability identified as CVE-2017-7187 represents a critical stack-based buffer overflow in the Linux kernel's SCSI generic (sg) subsystem, specifically within the sg_ioctl function located in drivers/scsi/sg.c. This flaw affects Linux kernel versions through 4.10.4 and exposes systems to potential denial of service conditions and unspecified security impacts. The vulnerability manifests when a local attacker executes an SG_NEXT_CMD_LEN ioctl call with an excessively large command size parameter, creating a scenario where the kernel's buffer handling mechanisms fail to properly validate input lengths before proceeding with operations.
The technical implementation of this vulnerability stems from inadequate bounds checking within the sg_ioctl function, which processes SCSI generic ioctl commands. When a maliciously crafted SG_NEXT_CMD_LEN ioctl call is made with an oversized command size, the kernel fails to validate that the specified buffer size remains within acceptable limits for stack allocation. This validation failure allows an attacker to manipulate the stack pointer and overwrite adjacent memory locations, resulting in out-of-bounds write operations that can corrupt kernel memory structures. The vulnerability is classified as a stack-based buffer overflow under CWE-121, which specifically addresses buffer overflow conditions where insufficient bounds checking permits writes beyond the allocated stack buffer boundaries.
The operational impact of CVE-2017-7187 extends beyond simple denial of service scenarios, as the out-of-bounds write operations can potentially lead to system instability, arbitrary code execution, or information disclosure. Local attackers with minimal privileges can exploit this vulnerability to crash the kernel, causing system-wide denial of service, or in more sophisticated attack scenarios, potentially escalate privileges by corrupting kernel memory structures. The vulnerability aligns with ATT&CK technique T1068, which covers 'Exploitation for Privilege Escalation,' as local users can leverage this flaw to gain elevated system privileges. Additionally, the vulnerability demonstrates characteristics of T1499.004, 'File Deletion,' through potential system crashes that could result in data loss or corruption during system recovery processes.
Mitigation strategies for CVE-2017-7187 primarily involve applying the official kernel patches released by the Linux kernel development team, which include enhanced input validation and proper bounds checking in the sg_ioctl function. System administrators should prioritize updating to kernel versions 4.10.5 or later, where the vulnerability has been addressed through code modifications that enforce strict validation of ioctl command sizes before buffer allocation. Organizations should also implement monitoring solutions to detect anomalous ioctl activity patterns that might indicate exploitation attempts. The patch implementation addresses the root cause by introducing proper size validation checks that prevent oversized command sizes from being processed, thereby eliminating the stack buffer overflow condition. Security teams should conduct vulnerability assessments to identify systems running affected kernel versions and establish automated patch management processes to ensure timely remediation across all production environments.