CVE-2018-12232 in Linux
Summary
by MITRE
In net/socket.c in the Linux kernel through 4.17.1, there is a race condition between fchownat and close in cases where they target the same socket file descriptor, related to the sock_close and sockfs_setattr functions. fchownat does not increment the file descriptor reference count, which allows close to set the socket to NULL during fchownat's execution, leading to a NULL pointer dereference and system crash.
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Analysis
by VulDB Data Team • 03/22/2023
The vulnerability described in CVE-2018-12232 represents a critical race condition within the Linux kernel's socket handling mechanism that exists in versions through 4.17.1. This flaw manifests in the interaction between the fchownat system call and the close operation when both target the same socket file descriptor, creating a scenario where concurrent execution can lead to system instability. The root cause lies in the improper handling of reference counting within the socket file descriptor management subsystem, specifically in how the fchownat function interacts with the socket close mechanism.
The technical implementation of this vulnerability stems from the sock_close and sockfs_setattr functions within the kernel's networking subsystem. When fchownat is executed against a socket file descriptor, it fails to increment the file descriptor reference count as required by proper kernel synchronization practices. This omission creates a window of vulnerability where the close operation can execute concurrently and set the socket structure pointer to NULL while fchownat is still processing. The subsequent dereference of this NULL pointer during fchownat's execution results in immediate system crash or potential privilege escalation depending on exploitation circumstances.
This race condition has significant operational impact on Linux systems, particularly those running kernel versions affected by this vulnerability. The vulnerability can be exploited by unprivileged users to cause system crashes, leading to denial of service conditions that compromise system availability. From a cybersecurity perspective, this flaw aligns with CWE-362, which specifically addresses race conditions in concurrent programming, and can be mapped to ATT&CK technique T1499.004 for system disruption. The vulnerability affects the core socket functionality of the Linux kernel, making it particularly dangerous as it can impact network services, system stability, and overall operational continuity.
The mitigation strategy for this vulnerability requires immediate kernel updates to versions that contain the patched implementation of socket file descriptor handling. System administrators should prioritize applying security patches that address the reference counting issue in sock_close and sockfs_setattr functions. Additionally, monitoring systems should be configured to detect unusual patterns of socket operations that might indicate exploitation attempts. The fix typically involves ensuring proper reference counting mechanisms are in place during concurrent socket operations, preventing the NULL pointer dereference scenario that leads to system crashes. Organizations should also implement proper kernel hardening measures and consider using security modules like SELinux or AppArmor to further restrict potential exploitation vectors.