[dm-devel] [RFC 2/7] dm: measure data on device resume

[Tushar Sugandhi]

A given block device can load a table multiple times, with different
input parameters, before eventually resuming it.  Further, a device may
be suspended and then resumed.  The device may never resume after a
table-load.  Because of the above valid scenarios for a given device,
it is important to measure and log the device resume event using IMA.

Also, if the table is large, measuring it in clear-text each time the
device changes state, will unnecessarily increase the size of IMA log.
Since the table clear-text is already measured during table-load event,
measuring the hash during resume should be sufficient to validate the
table contents.

Measure the device parameters, and hash of the active table, when the
device is resumed.

Signed-off-by: Tushar Sugandhi <tusharsu at linux.microsoft.com>
---
 drivers/md/dm-ima.c   | 47 +++++++++++++++++++++++++++++++++++++++++++
 drivers/md/dm-ima.h   |  1 +
 drivers/md/dm-ioctl.c |  8 ++++++--
 3 files changed, 54 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c
index 8903e746ead6..b244a7fd58fe 100644
--- a/drivers/md/dm-ima.c
+++ b/drivers/md/dm-ima.c
@@ -211,8 +211,55 @@ void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_fl
 	kfree(ima_buf_head);
 }
 
+/*
+ * Measure IMA data on device resume
+ */
+void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap)
+{
+	char *device_table_data;
+	unsigned int noio_flag, l;
+	char active[] = "active_table_hash=";
+	unsigned int active_len = strlen(active);
+
+	noio_flag = memalloc_noio_save();
+	device_table_data = kzalloc(DM_IMA_DEVICE_BUF_LEN, GFP_KERNEL);
+	memalloc_noio_restore(noio_flag);
+
+	if (!device_table_data)
+		return;
+
+	if (swap) {
+		kfree(md->ima.active_table_hash);
+		md->ima.active_table_hash = NULL;
+		md->ima.active_table_hash_len = 0;
+
+		if (md->ima.inactive_table_hash) {
+			md->ima.active_table_hash = md->ima.inactive_table_hash;
+			md->ima.active_table_hash_len = md->ima.inactive_table_hash_len;
+			md->ima.inactive_table_hash = NULL;
+			md->ima.inactive_table_hash_len = 0;
+		}
+	}
+
+	l = md->ima.device_data_len;
+	memcpy(device_table_data, md->ima.device_data, l);
+	memcpy(device_table_data + l, active, active_len);
+	l += active_len;
+
+	memcpy(device_table_data + l, md->ima.active_table_hash, md->ima.active_table_hash_len);
+	l += md->ima.active_table_hash_len;
+
+	memcpy(device_table_data + l, ";", 1);
+	l++;
+
+	dm_ima_measure_data("device_resume", device_table_data, l);
+
+	kfree(device_table_data);
+}
+
 #else
 void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags) {}
+void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap) {}
 #endif
 MODULE_AUTHOR("Tushar Sugandhi <tusharsu at linux.microsoft.com>");
 MODULE_DESCRIPTION("Enables IMA measurements for DM targets");
diff --git a/drivers/md/dm-ima.h b/drivers/md/dm-ima.h
index a71e0682fcb9..1cd0c76e0379 100644
--- a/drivers/md/dm-ima.h
+++ b/drivers/md/dm-ima.h
@@ -33,4 +33,5 @@ struct dm_ima_measurements {
 };
 
 void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags);
+void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap);
 #endif /*DM_IMA_H*/
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 21deff8513a7..e06e256d1a7e 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1162,8 +1162,12 @@ static int do_resume(struct dm_ioctl *param)
 
 	if (dm_suspended_md(md)) {
 		r = dm_resume(md);
-		if (!r && !dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr))
-			param->flags |= DM_UEVENT_GENERATED_FLAG;
+		if (!r) {
+			dm_ima_measure_on_device_resume(md, new_map ? true : false);
+
+			if (!dm_kobject_uevent(md, KOBJ_CHANGE, param->event_nr))
+				param->flags |= DM_UEVENT_GENERATED_FLAG;
+		}
 	}
 
 	/*
-- 
2.17.1