ksmbd: fix slab-use-after-free in smb3_preauth_hash_rsp

ksmbd_user_session_put should be called under smb3_preauth_hash_rsp().
It will avoid freeing session before calling smb3_preauth_hash_rsp().

Cc: stable@vger.kernel.org # v5.15+
Reported-by: Norbert Szetei <norbert@doyensec.com>
Tested-by: Norbert Szetei <norbert@doyensec.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

Author: namjaejeon

fs/smb/server/server.c

@@ -238,11 +238,11 @@ static void __handle_ksmbd_work(struct ksmbd_work *work,
 	} while (is_chained == true);
 
 send:
-	if (work->sess)
-		ksmbd_user_session_put(work->sess);
 	if (work->tcon)
 		ksmbd_tree_connect_put(work->tcon);
 	smb3_preauth_hash_rsp(work);
+	if (work->sess)
+		ksmbd_user_session_put(work->sess);
 	if (work->sess && work->sess->enc && work->encrypted &&
 	    conn->ops->encrypt_resp) {
 		rc = conn->ops->encrypt_resp(work);