CVE-2026-72315

/// Technical description

In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix busy dentry warning on unmount after DIO

Commit c68337442f03 ("cifs: Fix busy dentry used after unmounting") fixed

the issue in cifs where deferred close of a file led to a dentry reference

count not being released in umount, by flushing deferredclose_wq in

cifs_kill_sb() to solve it.

However, the cifs DIO path suffers from the same busy-dentry problem caused

by a delayed dentry reference-count release:

[dio] [cifsd] [close + umount]

netfs_unbuffered_write_iter_locked

...

cifs_demultiplex_thread

netfs_unbuffered_write

cifs_issue_write

netfs_wait_for_in_progress_stream [1]

...

netfs_write_subrequest_terminated

netfs_subreq_clear_in_progress

netfs_wake_collector // wake [1]

netfs_put_subrequest

netfs_put_request

queue_work(system_dfl_wq, xxx) [2]

// dio write return cifs_close

_cifsFileInfo_put

// cfile->count 2->1

--cfile->c

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References