CVE-2016-10741 in Linux
Summary
by MITRE
In the Linux kernel before 4.9.3, fs/xfs/xfs_aops.c allows local users to cause a denial of service (system crash) because there is a race condition between direct and memory-mapped I/O (associated with a hole) that is handled with BUG_ON instead of an I/O failure.
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Analysis
by VulDB Data Team • 07/04/2023
The vulnerability described in CVE-2016-10741 represents a critical race condition flaw within the Linux kernel's XFS file system implementation that can lead to system crashes and denial of service conditions. This issue specifically affects kernel versions prior to 4.9.3 and stems from improper handling of concurrent direct I/O and memory-mapped I/O operations when dealing with file holes. The flaw manifests in the fs/xfs/xfs_aops.c source file where the kernel encounters a situation where a BUG_ON macro is invoked instead of properly handling the I/O failure scenario, resulting in immediate system termination.
The technical nature of this vulnerability involves a race condition that occurs when multiple I/O operations attempt to access the same file region simultaneously, particularly when that region contains a hole in the file data. Direct I/O operations and memory-mapped I/O operations interact in an unpredictable manner when they encounter such file holes, creating a scenario where the kernel's internal state becomes inconsistent. The BUG_ON macro, which is typically used for debugging purposes to catch unexpected conditions during kernel development, is triggered in production code instead of being replaced with proper error handling. This design flaw means that when the race condition occurs, the kernel cannot gracefully handle the error and instead crashes the entire system.
This vulnerability impacts system availability and can be exploited by local users who have access to the system, making it particularly concerning in multi-user environments where privilege escalation is not required. The operational impact extends beyond simple system crashes, as the denial of service can occur at any time during normal file system operations, potentially affecting critical system processes and applications that rely on XFS file system stability. The vulnerability is classified under CWE-362, which deals with race conditions, and aligns with ATT&CK technique T1499.004 for network denial of service, though in this case the attack vector is local rather than network-based. The flaw demonstrates a fundamental issue in kernel design where development-time debugging macros are improperly deployed in production code paths.
Mitigation strategies for this vulnerability involve upgrading to Linux kernel version 4.9.3 or later where the race condition has been properly addressed through corrected error handling mechanisms. System administrators should prioritize patching affected systems, particularly those running XFS file systems in production environments where reliability is critical. Additionally, monitoring for unusual system crashes or I/O errors may help identify potential exploitation attempts, though the vulnerability itself does not require network access for exploitation. The fix implemented in the kernel version 4.9.3 properly handles the concurrent I/O operations by ensuring that I/O failures are returned appropriately rather than causing kernel panics, thereby maintaining system stability while preserving the intended functionality of both direct and memory-mapped I/O operations.