CVE-2008-2137 in Linux
Summary
by MITRE
The (1) sparc_mmap_check function in arch/sparc/kernel/sys_sparc.c and the (2) sparc64_mmap_check function in arch/sparc64/kernel/sys_sparc.c, in the Linux kernel 2.4 before 2.4.36.5 and 2.6 before 2.6.25.3, omit some virtual-address range (aka span) checks when the mmap MAP_FIXED bit is not set, which allows local users to cause a denial of service (panic) via unspecified mmap calls.
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Analysis
by VulDB Data Team • 08/10/2019
The vulnerability described in CVE-2008-2137 represents a critical flaw in the Linux kernel's memory management subsystem affecting SPARC architecture implementations. This issue exists in both 32-bit and 64-bit SPARC kernel variants, specifically impacting kernel versions prior to 2.4.36.5 and 2.6.25.3. The flaw manifests in two distinct functions: sparc_mmap_check in the 32-bit kernel and sparc64_mmap_check in the 64-bit kernel, both located within the kernel's system call handling code. These functions are responsible for validating memory mapping operations and ensuring proper virtual address range checking during mmap system calls.
The technical root cause of this vulnerability lies in the improper implementation of virtual address range validation when the MAP_FIXED flag is not explicitly set during memory mapping operations. Under normal circumstances, when MAP_FIXED is not specified, the kernel should perform comprehensive span checks to prevent memory mapping operations from inadvertently overlapping or corrupting existing memory regions. However, the flawed implementation in these kernel versions omits these crucial range validation checks, creating a scenario where malicious or malformed mmap calls can bypass normal memory management safeguards. This omission effectively allows attackers to manipulate virtual address spaces in ways that were not intended by the kernel's memory management design.
The operational impact of this vulnerability is severe, as it enables local users to trigger kernel panics through carefully crafted mmap system calls. The denial of service condition occurs when the kernel encounters memory mapping operations that violate its expected address space constraints, leading to system instability and potential complete system crashes. This vulnerability is particularly dangerous because it affects the kernel's core memory management functions, which are fundamental to system operation. The panic conditions can result in complete system shutdowns, requiring manual intervention to restore normal operation, and may even leave systems in an unrecoverable state.
From a cybersecurity perspective, this vulnerability aligns with CWE-129, which addresses improper validation of input ranges, and represents a classic example of insufficient input validation in kernel space. The flaw also relates to ATT&CK technique T1499.004, which involves network denial of service attacks through kernel-level vulnerabilities. The vulnerability's exploitation requires local system access, making it a privilege escalation concern that could potentially be leveraged by attackers who have already gained system-level access. Organizations should prioritize patching this vulnerability as it represents a fundamental weakness in kernel memory management that could be exploited to disrupt system availability.
The recommended mitigation strategy involves immediate upgrading of affected kernel versions to the patched releases 2.4.36.5 and 2.6.25.3, which contain the necessary fixes to properly implement virtual address range checks in both sparc_mmap_check and sparc64_mmap_check functions. System administrators should also implement monitoring solutions to detect unusual mmap activity patterns that might indicate exploitation attempts. Additionally, organizations should conduct thorough vulnerability assessments to ensure all SPARC-based systems are properly patched and consider implementing kernel hardening measures such as address space layout randomization and enhanced memory protection mechanisms to further reduce the attack surface.