[PATCH 1/2] iscsi_tcp: do not bind sockets that already have extra callbacks

[Khazhismel Kumykov <khazhy@chromium.org>]

This attempts to avoid a situation where a misbehaving iscsi daemon
passes a socket for a different iSCSI connection to BIND_CONN - which
would result in infinite recursion and stack overflow. This will
also prevent passing *other* sockets which had sk_user_data overridden,
but that wouldn't have been safe anyways - since we throw away that
pointer anyways. This does not cover all hypothetical scenarios where we
pass bad sockets to BIND_CONN.

This also papers over a different bug - we allow a daemon to call
BIND_CONN twice for the same connection - which would result in, at the
least, failing to uninitialize/teardown the previous socket, which will
be addressed separately.

Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
 drivers/scsi/iscsi_tcp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 8e14cea15f98..e8ed60b777c6 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -725,7 +725,7 @@ iscsi_sw_tcp_conn_bind(struct iscsi_cls_session *cls_session,
 	}
 
 	err = -EINVAL;
-	if (!sk_is_tcp(sock->sk))
+	if (!sk_is_tcp(sock->sk) || sock->sk->sk_user_data)
 		goto free_socket;
 
 	err = iscsi_conn_bind(cls_session, cls_conn, is_leading);
-- 
2.44.0.291.gc1ea87d7ee-goog