SMB3: Do not send lease break acknowledgment if all file handles have been closed

jira VULN-131073
cve-pre CVE-2025-38527
commit-author Bharath SM <[email protected]>
commit da787d5

In case if all existing file handles are deferred handles and if all of
them gets closed due to handle lease break then we dont need to send
lease break acknowledgment to server, because last handle close will be
considered as lease break ack.
After closing deferred handels, we check for openfile list of inode,
if its empty then we skip sending lease break ack.

Fixes: 59a556a ("SMB3: drop reference to cfile before sending oplock break")
	Reviewed-by: Tom Talpey <[email protected]>
	Signed-off-by: Bharath SM <[email protected]>
	Signed-off-by: Steve French <[email protected]>
(cherry picked from commit da787d5)
	Signed-off-by: Brett Mastbergen <[email protected]>

Author: bmastbergen

fs/cifs/file.c

@@ -5106,20 +5106,19 @@ void cifs_oplock_break(struct work_struct *work)
 
 	_cifsFileInfo_put(cfile, false /* do not wait for ourself */, false);
 	/*
-	 * releasing stale oplock after recent reconnect of smb session using
-	 * a now incorrect file handle is not a data integrity issue but do
-	 * not bother sending an oplock release if session to server still is
-	 * disconnected since oplock already released by the server
+	 * MS-SMB2 3.2.5.19.1 and 3.2.5.19.2 (and MS-CIFS 3.2.5.42) do not require
+	 * an acknowledgment to be sent when the file has already been closed.
+	 * check for server null, since can race with kill_sb calling tree disconnect.
 	 */
-	if (!oplock_break_cancelled) {
-		/* check for server null since can race with kill_sb calling tree disconnect */
-		if (tcon->ses && tcon->ses->server) {
-			rc = tcon->ses->server->ops->oplock_response(tcon, persistent_fid,
-				volatile_fid, net_fid, cinode);
-			cifs_dbg(FYI, "Oplock release rc = %d\n", rc);
-		} else
-			pr_warn_once("lease break not sent for unmounted share\n");
-	}
+	spin_lock(&cinode->open_file_lock);
+	if (tcon->ses && tcon->ses->server && !oplock_break_cancelled &&
+					!list_empty(&cinode->openFileList)) {
+		spin_unlock(&cinode->open_file_lock);
+		rc = tcon->ses->server->ops->oplock_response(tcon, persistent_fid,
+						volatile_fid, net_fid, cinode);
+		cifs_dbg(FYI, "Oplock release rc = %d\n", rc);
+	} else
+		spin_unlock(&cinode->open_file_lock);
 
 	cifs_done_oplock_break(cinode);
 }