CVE-2026-97557 in Linux
الملخص
بحسب MITRE • 25/09/2026
In the Linux kernel, the following vulnerability has been resolved:
smb: client: avoid leaking refcount in cifs_queue_oplock_break()
cifs_queue_oplock_break() unconditionally takes a reference on the target file before queueing cifs_oplock_break(). Only that work item decreases the reference counter again.
If another oplock break arrives while that work is still queued, queue_work() will return false and not queue this second work item. As a result, we will never reach the point to drop the file reference again and are leaking this reference. This can be triggered when interacting with a slow-responding server.
As a result, later unmount operations for this file system will fail with
BUG: Dentry ... still in use (1) [unmount of cifs cifs]
VFS: Busy inodes after unmount of cifs (cifs) kernel BUG at fs/super.c:777!
Fix this by only incrementing the reference count if the work has been queued successfully. Taking it after queue_work() is safe because all three callers hold tcon->open_file_lock across the call and _cifsFileInfo_put() decrements under that same lock, so a worker that starts the handler in the window cannot drop the reference before it has been taken.
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