CVE-2026-97557smb: client: avoid leaking refcount in cifs_queue_oplock_break()

Official description

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.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/13b9519b19e6e58a6cd01e63062cd1da7bd6449a
• https://git.kernel.org/stable/c/0fb92ac85db58945ad7b970ff17674001487b3a3
• https://git.kernel.org/stable/c/735a3a610136ae10f381d0909dff38e5b5c5f056
• https://git.kernel.org/stable/c/de2a6bcff2659bea40c7485115b57f0ae189fc01
• https://git.kernel.org/stable/c/af0193bbf1ac8c0f67f972998b0cc629d6116cf6
• https://git.kernel.org/stable/c/2ed2c29dd9593637cfa25ac1eb23241b20202778
• https://git.kernel.org/stable/c/dfe7b750c7e069873a8a57a11c816831a235618a
• https://git.kernel.org/stable/c/9f2e63f1b2d5fc5b5423424902c091123e220e7e