target: Fix SPC-2 RELEASE bug for multi-session iSCSI client setups

commit edc318d upstream.

This patch addresses a bug in a special case for target core SPC-2 RELEASE
logic where the same physical client (eg: iSCSI InitiatorName) with
differing iSCSI session identifiers (ISID) is allowed to incorrectly release
the same client's SPC-2 reservation from the non reservation holding path.

Note this bug is specific to iscsi-target w/ SPC-2 reservations, and
with the default enforce_pr_isids=1 device attr setting in target-core
controls if a InitiatorName + different ISID reservations are handled
the same as a single iSCSI client entity.

Signed-off-by: Bernhard Kohl <bernhard.kohl@gmx.net>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/target/target_core_pr.c

@@ -223,6 +223,9 @@ int target_scsi2_reservation_release(struct se_task *task)
 	if (dev->dev_reserved_node_acl != sess->se_node_acl)
 		goto out_unlock;
 
+	if (dev->dev_res_bin_isid != sess->sess_bin_isid)
+		goto out_unlock;
+
 	dev->dev_reserved_node_acl = NULL;
 	dev->dev_flags &= ~DF_SPC2_RESERVATIONS;
 	if (dev->dev_flags & DF_SPC2_RESERVATIONS_WITH_ISID) {