CVE-2025-38321

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

smb: Log an error when close_all_cached_dirs fails

Under low-memory conditions, close_all_cached_dirs() can't move the dentries to a separate list to dput() them once the locks are dropped. This will result in a "Dentry still in use" error, so add an error message that makes it clear this is what happened:

[ 495.281119] CIFS: VFS: \otters.example.com\share Out of memory while dropping dentries [ 495.281595] ------------[ cut here ]------------ [ 495.281887] BUG: Dentry ffff888115531138{i=78,n=/} still in use (2) [unmount of cifs cifs] [ 495.282391] WARNING: CPU: 1 PID: 2329 at fs/dcache.c:1536 umount_check+0xc8/0xf0

Also, bail out of looping through all tcons as soon as a single allocation fails, since we're already in trouble, and kmalloc() attempts for subseqeuent tcons are likely to fail just like the first one did.

This vulnerability is rated as Moderate severity because triggering the issue requires severe memory exhaustion during the unmounting of an active CIFS/SMB filesystem share, resulting in a denial of service. Systems that do not mount remote SMB network shares remain unaffected. In typical enterprise deployments, mounting and unmounting network shares requires administrative privileges, which substantially restricts potential exposure.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.