CVE-2010-3015 in Linux
Summary
by MITRE
Integer overflow in the ext4_ext_get_blocks function in fs/ext4/extents.c in the Linux kernel before 2.6.34 allows local users to cause a denial of service (BUG and system crash) via a write operation on the last block of a large file, followed by a sync operation.
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Analysis
by VulDB Data Team • 09/23/2021
The vulnerability identified as CVE-2010-3015 represents a critical integer overflow flaw within the Linux kernel's ext4 filesystem implementation that can be exploited to cause system-wide denial of service conditions. This issue resides in the ext4_ext_get_blocks function located in fs/ext4/extents.c, where the kernel fails to properly validate integer values during block allocation operations for large files. The vulnerability specifically manifests when a local user performs a write operation to the final block of an extremely large file, followed by a sync operation that triggers the flawed code path. The integer overflow occurs during the calculation of block extents, leading to incorrect memory management and ultimately causing the kernel to BUG and crash the entire system.
The technical nature of this vulnerability aligns with CWE-190, which describes integer overflow conditions that can result in memory corruption and system instability. The flaw exploits the kernel's handling of file extent management where the ext4 filesystem maintains metadata about file blocks in a structured format. When dealing with large files near the maximum addressable limits, the integer arithmetic used to calculate the number of blocks or extents fails to properly check for overflow conditions, causing the kernel to interpret corrupted values as valid memory addresses or block counts. This misinterpretation leads to memory corruption that manifests as kernel panics and system crashes, effectively rendering the entire system unavailable to legitimate users.
From an operational perspective, this vulnerability presents a significant risk to systems running Linux kernels prior to version 2.6.34, particularly in environments where large file operations are common or where local privilege escalation is possible. The attack vector requires local user access, making it less severe than remote exploits, but still highly problematic in multi-user environments or when combined with other vulnerabilities. The impact extends beyond simple service disruption as the kernel BUG and system crash can result in data loss, corrupted filesystem metadata, and extended downtime. The vulnerability can be triggered through routine file operations, making it particularly dangerous as it may be exploited by malicious users with local access or through compromised accounts.
The exploitation of this vulnerability follows patterns consistent with ATT&CK technique T1499.004, which involves system disruption through resource exhaustion or corruption. The mitigation strategy centers on upgrading to kernel versions 2.6.34 or later where the integer overflow has been patched. System administrators should also implement monitoring for unusual file system activity patterns that might indicate exploitation attempts. Additional defensive measures include restricting local user privileges where possible, implementing proper filesystem quotas, and maintaining regular kernel updates as part of standard security maintenance procedures. The patch for this vulnerability specifically addresses the integer overflow in the extent calculation logic, ensuring that proper bounds checking is performed before any arithmetic operations that could lead to overflow conditions. Organizations should prioritize this patch deployment given the potential for system-wide outages and the relatively straightforward nature of the fix.