[PATCH v2 2/2] scsi: iscsi_tcp: Fix UAF during login when accessing the shost ipaddress

[Mike Christie <michael.christie@xxxxxxxxxx>]

If during iscsi_sw_tcp_session_create iscsi_tcp_r2tpool_alloc fails
userspace could be accessing the host's ipaddress attr. If we then
free the session via iscsi_session_teardown while userspace is still
accessing the session we will hit a use after free bug.

This patch has us set the tcp_sw_host->session after we have completed
session creation and can no longer fail.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
 drivers/scsi/iscsi_tcp.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
index 9c0c8f34ef67..c3ad04ad66e0 100644
--- a/drivers/scsi/iscsi_tcp.c
+++ b/drivers/scsi/iscsi_tcp.c
@@ -848,7 +848,7 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
 				       enum iscsi_host_param param, char *buf)
 {
 	struct iscsi_sw_tcp_host *tcp_sw_host = iscsi_host_priv(shost);
-	struct iscsi_session *session = tcp_sw_host->session;
+	struct iscsi_session *session;
 	struct iscsi_conn *conn;
 	struct iscsi_tcp_conn *tcp_conn;
 	struct iscsi_sw_tcp_conn *tcp_sw_conn;
@@ -858,6 +858,7 @@ static int iscsi_sw_tcp_host_get_param(struct Scsi_Host *shost,
 
 	switch (param) {
 	case ISCSI_HOST_PARAM_IPADDRESS:
+		session = tcp_sw_host->session;
 		if (!session)
 			return -ENOTCONN;
 
@@ -958,11 +959,13 @@ iscsi_sw_tcp_session_create(struct iscsi_endpoint *ep, uint16_t cmds_max,
 	if (!cls_session)
 		goto remove_host;
 	session = cls_session->dd_data;
-	tcp_sw_host = iscsi_host_priv(shost);
-	tcp_sw_host->session = session;
 
 	if (iscsi_tcp_r2tpool_alloc(session))
 		goto remove_session;
+
+	/* We are now fully setup so expose the session to sysfs. */
+	tcp_sw_host = iscsi_host_priv(shost);
+	tcp_sw_host->session = session;
 	return cls_session;
 
 remove_session:
-- 
2.25.1