dm ima: measure data on device resume

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@linux.microsoft.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

3 files changed, 125 insertions, 2 deletions

diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c
index c8f54d9f6c8d..30b9875be63a 100644
--- a/drivers/md/dm-ima.c
+++ b/drivers/md/dm-ima.c
@@ -143,6 +143,26 @@ static void dm_ima_measure_data(const char *event_name, const void *buf, size_t
 }
 
 /*
+ * Internal function to allocate and copy current device capacity for IMA measurements.
+ */
+static int dm_ima_alloc_and_copy_capacity_str(struct mapped_device *md, char **capacity_str,
+					      bool noio)
+{
+	sector_t capacity;
+
+	capacity = get_capacity(md->disk);
+
+	*capacity_str = dm_ima_alloc(DM_IMA_DEVICE_CAPACITY_BUF_LEN, GFP_KERNEL, noio);
+	if (!(*capacity_str))
+		return -ENOMEM;
+
+	scnprintf(*capacity_str, DM_IMA_DEVICE_BUF_LEN, "current_device_capacity=%llu;",
+		  capacity);
+
+	return 0;
+}
+
+/*
  * Initialize/reset the dm ima related data structure variables.
  */
 void dm_ima_reset_data(struct mapped_device *md)
@@ -328,3 +348,99 @@ exit:
 	kfree(target_metadata_buf);
 	kfree(target_data_buf);
 }
+
+/*
+ * Measure IMA data on device resume.
+ */
+void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap)
+{
+	char *device_table_data, *dev_name = NULL, *dev_uuid = NULL, *capacity_str = NULL;
+	char active[] = "active_table_hash=";
+	unsigned int active_len = strlen(active), capacity_len = 0;
+	unsigned int l = 0;
+	bool noio = true;
+	int r;
+
+	device_table_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN, GFP_KERNEL, noio);
+	if (!device_table_data)
+		return;
+
+	r = dm_ima_alloc_and_copy_capacity_str(md, &capacity_str, noio);
+	if (r)
+		goto error;
+
+	if (swap) {
+		if (md->ima.active_table.hash != md->ima.inactive_table.hash)
+			kfree(md->ima.active_table.hash);
+
+		md->ima.active_table.hash = NULL;
+		md->ima.active_table.hash_len = 0;
+
+		if (md->ima.active_table.device_metadata !=
+		    md->ima.inactive_table.device_metadata)
+			kfree(md->ima.active_table.device_metadata);
+
+		md->ima.active_table.device_metadata = NULL;
+		md->ima.active_table.device_metadata_len = 0;
+		md->ima.active_table.num_targets = 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;
+		}
+
+		if (md->ima.inactive_table.device_metadata) {
+			md->ima.active_table.device_metadata =
+				md->ima.inactive_table.device_metadata;
+			md->ima.active_table.device_metadata_len =
+				md->ima.inactive_table.device_metadata_len;
+			md->ima.active_table.num_targets = md->ima.inactive_table.num_targets;
+			md->ima.inactive_table.device_metadata = NULL;
+			md->ima.inactive_table.device_metadata_len = 0;
+			md->ima.inactive_table.num_targets = 0;
+		}
+	}
+
+	if (md->ima.active_table.device_metadata) {
+		l = md->ima.active_table.device_metadata_len;
+		memcpy(device_table_data, md->ima.active_table.device_metadata, l);
+	}
+
+	if (md->ima.active_table.hash) {
+		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++;
+	}
+
+	if (!l) {
+		r = dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio);
+		if (r)
+			goto error;
+
+		scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
+			  "name=%s,uuid=%s;device_resume=no_data;",
+			  dev_name, dev_uuid);
+		l += strlen(device_table_data);
+
+	}
+
+	capacity_len = strlen(capacity_str);
+	memcpy(device_table_data + l, capacity_str, capacity_len);
+	l += capacity_len;
+
+	dm_ima_measure_data("device_resume", device_table_data, l, noio);
+
+	kfree(dev_name);
+	kfree(dev_uuid);
+error:
+	kfree(capacity_str);
+	kfree(device_table_data);
+}
diff --git a/drivers/md/dm-ima.h b/drivers/md/dm-ima.h
index 16afd9a8c0b2..78c36b877ccf 100644
--- a/drivers/md/dm-ima.h
+++ b/drivers/md/dm-ima.h
@@ -15,6 +15,7 @@
 #define DM_IMA_DEVICE_BUF_LEN		1024
 #define DM_IMA_TARGET_METADATA_BUF_LEN	128
 #define DM_IMA_TARGET_DATA_BUF_LEN	2048
+#define DM_IMA_DEVICE_CAPACITY_BUF_LEN	128
 
 #ifdef CONFIG_IMA
 
@@ -48,11 +49,13 @@ struct dm_ima_measurements {
 
 void dm_ima_reset_data(struct mapped_device *md);
 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);
 
 #else
 
 static inline void dm_ima_reset_data(struct mapped_device *md) {}
 static inline void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags) {}
+static inline void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap) {}
 
 #endif /* CONFIG_IMA */
 
diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index d7c3456bf858..100745cd8f01 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1160,8 +1160,12 @@ 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;
+		}
 	}
 
 	/*