ksmbd: fix race condition between destroy_previous_session() and smb2 operations()

If there is ->PreviousSessionId field in the session setup request,
The session of the previous connection should be destroyed.
During this, if the smb2 operation requests in the previous session are
being processed, a racy issue could happen with ksmbd_destroy_file_table().
This patch sets conn->status to KSMBD_SESS_NEED_RECONNECT to block
incoming  operations and waits until on-going operations are complete
(i.e. idle) before desctorying the previous session.

Fixes: c8efcc786146 ("ksmbd: add support for durable handles v1/v2")
Cc: stable@vger.kernel.org # v6.6+
Reported-by: zdi-disclosures@trendmicro.com # ZDI-CAN-25040
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Steve French <stfrench@microsoft.com>

1 files changed, 33 insertions, 1 deletions

diff --git a/fs/smb/server/connection.c b/fs/smb/server/connection.c
index 09e1e7771592..7889df8112b4 100644
--- a/fs/smb/server/connection.c
+++ b/fs/smb/server/connection.c
@@ -165,11 +165,43 @@ void ksmbd_all_conn_set_status(u64 sess_id, u32 status)
 	up_read(&conn_list_lock);
 }
 
-void ksmbd_conn_wait_idle(struct ksmbd_conn *conn, u64 sess_id)
+void ksmbd_conn_wait_idle(struct ksmbd_conn *conn)
 {
 	wait_event(conn->req_running_q, atomic_read(&conn->req_running) < 2);
 }
 
+int ksmbd_conn_wait_idle_sess_id(struct ksmbd_conn *curr_conn, u64 sess_id)
+{
+	struct ksmbd_conn *conn;
+	int rc, retry_count = 0, max_timeout = 120;
+	int rcount = 1;
+
+retry_idle:
+	if (retry_count >= max_timeout)
+		return -EIO;
+
+	down_read(&conn_list_lock);
+	list_for_each_entry(conn, &conn_list, conns_list) {
+		if (conn->binding || xa_load(&conn->sessions, sess_id)) {
+			if (conn == curr_conn)
+				rcount = 2;
+			if (atomic_read(&conn->req_running) >= rcount) {
+				rc = wait_event_timeout(conn->req_running_q,
+					atomic_read(&conn->req_running) < rcount,
+					HZ);
+				if (!rc) {
+					up_read(&conn_list_lock);
+					retry_count++;
+					goto retry_idle;
+				}
+			}
+		}
+	}
+	up_read(&conn_list_lock);
+
+	return 0;
+}
+
 int ksmbd_conn_write(struct ksmbd_work *work)
 {
 	struct ksmbd_conn *conn = work->conn;