target: Add link_magic for fabric allow_link destination target_items

commit 0ff8754981261a80f4b77db2536dfea92c2d4539 upstream.

This patch adds [dev,lun]_link_magic value assignment + checks within generic
target_fabric_port_link() and target_fabric_mappedlun_link() code to ensure
destination config_item *target_item sent from configfs_symlink() ->
config_item_operations->allow_link() is the underlying se_device->dev_group
and se_lun->lun_group that we expect to symlink.

Reported-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>
Signed-off-by: CAI Qian <caiqian@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

5 files changed, 19 insertions, 0 deletions

diff --git a/drivers/target/target_core_device.c b/drivers/target/target_core_device.c
index 4df8022fe3c8..26c62f059754 100644
--- a/drivers/target/target_core_device.c
+++ b/drivers/target/target_core_device.c
@@ -1665,6 +1665,7 @@ int core_dev_setup_virtual_lun0(void)
 		ret = PTR_ERR(dev);
 		goto out;
 	}
+	dev->dev_link_magic = SE_DEV_LINK_MAGIC;
 	se_dev->se_dev_ptr = dev;
 	g_lun0_dev = dev;
 
diff --git a/drivers/target/target_core_fabric_configfs.c b/drivers/target/target_core_fabric_configfs.c
index 405cc98eaed6..b009b89d2fb4 100644
--- a/drivers/target/target_core_fabric_configfs.c
+++ b/drivers/target/target_core_fabric_configfs.c
@@ -72,6 +72,12 @@ static int target_fabric_mappedlun_link(
 	struct se_portal_group *se_tpg;
 	struct config_item *nacl_ci, *tpg_ci, *tpg_ci_s, *wwn_ci, *wwn_ci_s;
 	int ret = 0, lun_access;
+
+	if (lun->lun_link_magic != SE_LUN_LINK_MAGIC) {
+		pr_err("Bad lun->lun_link_magic, not a valid lun_ci pointer:"
+			" %p to struct lun: %p\n", lun_ci, lun);
+		return -EFAULT;
+	}
 	/*
 	 * Ensure that the source port exists
 	 */
@@ -746,6 +752,12 @@ static int target_fabric_port_link(
 	struct target_fabric_configfs *tf;
 	int ret;
 
+	if (dev->dev_link_magic != SE_DEV_LINK_MAGIC) {
+		pr_err("Bad dev->dev_link_magic, not a valid se_dev_ci pointer:"
+			" %p to struct se_device: %p\n", se_dev_ci, dev);
+		return -EFAULT;
+	}
+
 	tpg_ci = &lun_ci->ci_parent->ci_group->cg_item;
 	se_tpg = container_of(to_config_group(tpg_ci),
 				struct se_portal_group, tpg_group);
diff --git a/drivers/target/target_core_tpg.c b/drivers/target/target_core_tpg.c
index e320ec24aa1b..ba537b6fd85e 100644
--- a/drivers/target/target_core_tpg.c
+++ b/drivers/target/target_core_tpg.c
@@ -677,6 +677,7 @@ int core_tpg_register(
 	for (i = 0; i < TRANSPORT_MAX_LUNS_PER_TPG; i++) {
 		lun = se_tpg->tpg_lun_list[i];
 		lun->unpacked_lun = i;
+		lun->lun_link_magic = SE_LUN_LINK_MAGIC;
 		lun->lun_status = TRANSPORT_LUN_STATUS_FREE;
 		atomic_set(&lun->lun_acl_count, 0);
 		init_completion(&lun->lun_shutdown_comp);
diff --git a/drivers/target/target_core_transport.c b/drivers/target/target_core_transport.c
index f52e5a0041b4..f687892b00be 100644
--- a/drivers/target/target_core_transport.c
+++ b/drivers/target/target_core_transport.c
@@ -1341,6 +1341,7 @@ struct se_device *transport_add_device_to_core_hba(
 	dev->se_hba		= hba;
 	dev->se_sub_dev		= se_dev;
 	dev->transport		= transport;
+	dev->dev_link_magic	= SE_DEV_LINK_MAGIC;
 	INIT_LIST_HEAD(&dev->dev_list);
 	INIT_LIST_HEAD(&dev->dev_sep_list);
 	INIT_LIST_HEAD(&dev->dev_tmr_list);
diff --git a/include/target/target_core_base.h b/include/target/target_core_base.h
index 3ad5b33ee328..569c28236b09 100644
--- a/include/target/target_core_base.h
+++ b/include/target/target_core_base.h
@@ -779,6 +779,8 @@ struct se_subsystem_dev {
 };
 
 struct se_device {
+#define SE_DEV_LINK_MAGIC			0xfeeddeef
+	u32			dev_link_magic;
 	/* RELATIVE TARGET PORT IDENTIFER Counter */
 	u16			dev_rpti_counter;
 	/* Used for SAM Task Attribute ordering */
@@ -869,6 +871,8 @@ struct se_port_stat_grps {
 };
 
 struct se_lun {
+#define SE_LUN_LINK_MAGIC			0xffff7771
+	u32			lun_link_magic;
 	/* See transport_lun_status_table */
 	enum transport_lun_status_table lun_status;
 	u32			lun_access;