ksmbd: fix use-after-free in ksmbd_free_work_struct

->interim_entry of ksmbd_work could be deleted after oplock is freed.
We don't need to manage it with linked list. The interim request could be
immediately sent whenever a oplock break wait is needed.

Cc: [e-mail]
Reported-by: Norbert Szetei <[e-mail]>
Tested-by: Norbert Szetei <[e-mail]>
Signed-off-by: Namjae Jeon <[e-mail]>
Signed-off-by: Steve French <[e-mail]>

fs/smb/server/ksmbd_work.c

···
 		INIT_LIST_HEAD(&work->request_entry);
 		INIT_LIST_HEAD(&work->async_request_entry);
 		INIT_LIST_HEAD(&work->fp_entry);
-		INIT_LIST_HEAD(&work->interim_entry);
 		INIT_LIST_HEAD(&work->aux_read_list);
 		work->iov_alloc_cnt = 4;
 		work->iov = kcalloc(work->iov_alloc_cnt, sizeof(struct kvec),
···
 	kfree(work->tr_buf);
 	kvfree(work->request_buf);
 	kfree(work->iov);
-	if (!list_empty(&work->interim_entry))
-		list_del(&work->interim_entry);
 
 	if (work->async_id)
 		ksmbd_release_id(&work->conn->async_ida, work->async_id);

fs/smb/server/ksmbd_work.h

···
 	/* List head at conn->async_requests */
 	struct list_head                async_request_entry;
 	struct list_head                fp_entry;
-	struct list_head                interim_entry;
 };
 
 /**

fs/smb/server/oplock.c

···
 	opinfo->fid = id;
 	opinfo->Tid = Tid;
 	INIT_LIST_HEAD(&opinfo->op_entry);
-	INIT_LIST_HEAD(&opinfo->interim_list);
 	init_waitqueue_head(&opinfo->oplock_q);
 	init_waitqueue_head(&opinfo->oplock_brk);
 	atomic_set(&opinfo->refcount, 1);
···
 static int smb2_lease_break_noti(struct oplock_info *opinfo)
 {
 	struct ksmbd_conn *conn = opinfo->conn;
-	struct list_head *tmp, *t;
 	struct ksmbd_work *work;
 	struct lease_break_info *br_info;
 	struct lease *lease = opinfo->o_lease;
···
 	work->sess = opinfo->sess;
 
 	if (opinfo->op_state == OPLOCK_ACK_WAIT) {
-		list_for_each_safe(tmp, t, &opinfo->interim_list) {
-			struct ksmbd_work *in_work;
-
-			in_work = list_entry(tmp, struct ksmbd_work,
-					     interim_entry);
-			setup_async_work(in_work, NULL, NULL);
-			smb2_send_interim_resp(in_work, STATUS_PENDING);
-			list_del_init(&in_work->interim_entry);
-			release_async_work(in_work);
-		}
 		INIT_WORK(&work->work, __smb2_lease_break_noti);
 		ksmbd_queue_work(work);
 		wait_for_break_ack(opinfo);
···
 	}
 }
 
-static int oplock_break(struct oplock_info *brk_opinfo, int req_op_level)
+static int oplock_break(struct oplock_info *brk_opinfo, int req_op_level,
+			struct ksmbd_work *in_work)
 {
 	int err = 0;
 
···
 		}
 
 		if (lease->state & (SMB2_LEASE_WRITE_CACHING_LE |
-				SMB2_LEASE_HANDLE_CACHING_LE))
+				SMB2_LEASE_HANDLE_CACHING_LE)) {
+			if (in_work) {
+				setup_async_work(in_work, NULL, NULL);
+				smb2_send_interim_resp(in_work, STATUS_PENDING);
+				release_async_work(in_work);
+			}
+
 			brk_opinfo->op_state = OPLOCK_ACK_WAIT;
-		else
+		} else
 			atomic_dec(&brk_opinfo->breaking_cnt);
 	} else {
 		err = oplock_break_pending(brk_opinfo, req_op_level);
···
 			if (ksmbd_conn_releasing(opinfo->conn))
 				continue;
 
-			oplock_break(opinfo, SMB2_OPLOCK_LEVEL_NONE);
+			oplock_break(opinfo, SMB2_OPLOCK_LEVEL_NONE, NULL);
 			opinfo_put(opinfo);
 		}
 	}
···
 
 			if (ksmbd_conn_releasing(opinfo->conn))
 				continue;
-			oplock_break(opinfo, SMB2_OPLOCK_LEVEL_NONE);
+			oplock_break(opinfo, SMB2_OPLOCK_LEVEL_NONE, NULL);
 			opinfo_put(opinfo);
 		}
 	}
···
 		goto op_break_not_needed;
 	}
 
-	list_add(&work->interim_entry, &prev_opinfo->interim_list);
-	err = oplock_break(prev_opinfo, SMB2_OPLOCK_LEVEL_II);
+	err = oplock_break(prev_opinfo, SMB2_OPLOCK_LEVEL_II, work);
 	opinfo_put(prev_opinfo);
 	if (err == -ENOENT)
 		goto set_lev;
···
 	}
 
 	brk_opinfo->open_trunc = is_trunc;
-	list_add(&work->interim_entry, &brk_opinfo->interim_list);
-	oplock_break(brk_opinfo, SMB2_OPLOCK_LEVEL_II);
+	oplock_break(brk_opinfo, SMB2_OPLOCK_LEVEL_II, work);
 	opinfo_put(brk_opinfo);
 }
 
···
 			    SMB2_LEASE_KEY_SIZE))
 			goto next;
 		brk_op->open_trunc = is_trunc;
-		oplock_break(brk_op, SMB2_OPLOCK_LEVEL_NONE);
+		oplock_break(brk_op, SMB2_OPLOCK_LEVEL_NONE, NULL);
 next:
 		opinfo_put(brk_op);
 		rcu_read_lock();

fs/smb/server/oplock.h

···
 	bool			is_lease;
 	bool			open_trunc;	/* truncate on open */
 	struct lease		*o_lease;
-	struct list_head        interim_list;
 	struct list_head        op_entry;
 	struct list_head        lease_entry;
 	wait_queue_head_t oplock_q; /* Other server threads */