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How the mentioned CVE works (around 20 lines):
The vulnerability exists within the `qibfs` filesystem driver in the Linux kernel. When a process attempts to create a new file or directory in this specific filesystem, the kernel must allocate a new `inode` data structure to represent it. If the system is under severe memory pressure (OOM – Out Of Memory) and this `inode` allocation fails, the kernel’s error handling path is flawed. Instead of properly cleaning up all associated resources, the code leaks a `dentry` (directory entry) object that was already created earlier in the operation. This `dentry` object remains allocated in kernel memory but becomes unreachable and unusable. Each failed file creation attempt under these specific low-memory conditions will leak one dentry. While a single leak is small, an attacker with local access can repeatedly trigger this faulty code path. By deliberately exhausting memory to force allocation failures and then targeting the `qibfs` filesystem, they can cause sustained memory leakage. This gradual exhaustion of kernel memory resources can lead to a system-wide denial-of-service, as the kernel may eventually be unable to fulfill legitimate memory requests for other operations, potentially causing crashes or freezes.
Platform: Linux Kernel
Version: Up to fix
Vulnerability: Local Denial-of-Service
Severity: High
Date: 2025-05-20
Prediction: 2025-12-16
What Undercode Say:
Showing bash commands and codes related to the blog
`uname -r` – Check your kernel version.
`dmesg | grep -i “oom\|qibfs”` – Search system logs for Out-of-Memory or qibfs related errors.
Code logic from the fix: The patch ensures that on `inode` allocation failure in qibfs, the previously allocated `dentry` is properly released (dput) before returning the error.
How Exploit:
An attacker with local user access can repeatedly attempt to create files on the affected `qibfs` filesystem while also consuming large amounts of system memory to trigger OOM conditions and cause the vulnerable failure path, leading to a kernel memory leak and eventual denial-of-service.
Protection from this CVE:
Update the Linux kernel to a version that contains the commit fixing the `qibfs` dentry leak. Apply security patches from your Linux distribution vendor.
Impact:
Local denial-of-service via gradual kernel memory exhaustion, potentially causing system instability or crashes.
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Sources:
Reported By: nvd.nist.gov
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