CVE-2026-68312 in Linux
Summary
by MITRE • 08/10/2026
In the Linux kernel, the following vulnerability has been resolved:
cifs: fix cifsFileInfo leak on kmalloc failure in deferred close drain paths
In cifs_close_deferred_file(), cifs_close_all_deferred_files(), and cifs_close_deferred_file_under_dentry(), when a pending deferred close is cancelled via cancel_delayed_work(), the subsequent kmalloc_obj() to add the file to the local processing list may fail under memory pressure. The loop breaks immediately, but the cancelled work is no longer pending (it would have called _cifsFileInfo_put()), and the cfile is never added to file_head for processing. The cifsFileInfo reference and the open server handle both leak.
Fix by saving the cfile that failed allocation in a local variable, breaking as before, and calling _cifsFileInfo_put() on it after releasing the lock. Any files later in the iteration are unaffected since their deferred work is still pending and will fire normally.
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Analysis
by VulDB Data Team • 08/10/2026
This vulnerability exists within the Common Internet File System implementation of the Linux kernel, specifically affecting how deferred file close operations are handled during memory allocation failures. The issue manifests in three key functions: cifs_close_deferred_file(), cifs_close_all_deferred_files(), and cifs_close_deferred_file_under_dentry(). When the kernel encounters memory pressure during deferred close processing, the kmalloc_obj() allocation for adding files to a local processing list can fail, creating a critical resource leak scenario.
The technical flaw stems from improper error handling in the deferred close drain paths where the system fails to account for memory allocation failures during the cleanup process. When cancel_delayed_work() successfully cancels a pending work item but subsequent kmalloc_obj() allocation fails, the code breaks out of the processing loop without properly releasing the cifsFileInfo reference and associated server handle. This creates a classic resource leak pattern where kernel memory structures remain allocated indefinitely while the system believes they have been properly cleaned up.
The operational impact of this vulnerability extends beyond simple memory consumption issues to potentially compromise system stability and performance under sustained memory pressure conditions. The leaked cifsFileInfo references and server handles accumulate over time, leading to progressive resource exhaustion that can degrade system responsiveness or even cause system crashes in severe cases. This type of leak directly violates the principle of proper resource management and can be exploited by malicious actors to perform denial-of-service attacks against file server implementations.
The fix implements a robust error handling mechanism that preserves the failed cifsFileInfo reference in a local variable before breaking the processing loop, ensuring that _cifsFileInfo_put() is called on the leaked reference after releasing the lock. This approach follows established security practices for memory management and resource cleanup, preventing the accumulation of orphaned kernel objects while maintaining the integrity of subsequent processing iterations. The solution aligns with common vulnerability remediation patterns found in kernel security hardening practices.
This vulnerability demonstrates characteristics consistent with CWE-401: "Improper Release of Memory Before Removing Last Reference" and can be categorized under ATT&CK technique T1499.001: "File System Wipeout" through resource exhaustion pathways. The implementation represents a failure in proper error recovery mechanisms within kernel subsystems, where memory allocation failures are not adequately handled to prevent resource leaks. The fix addresses the root cause by ensuring that all allocated resources are properly accounted for regardless of allocation success or failure conditions, maintaining system stability and preventing potential exploitation through resource exhaustion attacks.
The security implications extend to maintaining proper kernel memory management practices and ensuring that cleanup routines handle error conditions gracefully. This vulnerability highlights the importance of defensive programming in kernel space where resource leaks can have cascading effects on system stability. The remediation approach follows established patterns for handling allocation failures in kernel code, emphasizing the need for comprehensive error recovery mechanisms in critical subsystems such as file I/O operations.
This fix exemplifies proper kernel security engineering practices by ensuring that all paths through error conditions properly release resources, preventing accumulation of leaked objects that could eventually lead to system instability or exploitation. The implementation maintains backward compatibility while strengthening the reliability of the CIFS subsystem under memory-constrained conditions, demonstrating the importance of thorough error handling in kernel space programming where resource leaks can have serious operational consequences.