CVE-2026-64108

/// Technical description

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

cifs: Fix busy dentry used after unmounting

Since commit 340cea84f691c ("cifs: open files should not hold ref on

superblock"), cifs file only holds the dentry ref_cnt, the cifs file

close work(cfile->deferred) could be executed after unmounting, which

will trigger a warning in generic_shutdown_super:

BUG: Dentry 00000000a14a6845{i=c,n=file} still in use (1) [unmount of

cifs cifs]

The detailed processs is:

process A process B kworker

fd = open(PATH)

vfs_open

file->__f_path = *path // dentry->d_lockref.count = 1

cifs_open

cifs_new_fileinfo

cfile->dentry = dget(dentry) // dentry->d_lockref.count = 2

close(fd)

__fput

cifs_close

queue_delayed_work(deferredclose_wq, cfile->deferred)

dput(dentry) // dentry->d_lockref.count = 1

smb2_deferred_work_close

_cifsFileInfo_put

list_del(&cifs_file->flist)

umount

clean

/// 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