dm ima: measure data on table clear

For a given block device, an inactive table slot contains the parameters
to configure the device with.  The inactive table can be cleared
multiple times, accidentally or maliciously, which may impact the
functionality of the device, and compromise the system.  Therefore it is
important to measure and log the event when a table is cleared.

Measure device parameters, and table hashes when the inactive table slot
is cleared.
Signed-off-by: Tushar Sugandhi <tusharsu@linux.microsoft.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-ima.c

@@ -563,3 +563,95 @@ void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all)
 	kfree(dev_name);
 	kfree(dev_uuid);
 }
+
+/*
+ * Measure ima data on table clear.
+ */
+void dm_ima_measure_on_table_clear(struct mapped_device *md, bool new_map)
+{
+	unsigned int l = 0, capacity_len = 0;
+	char *device_table_data = NULL, *dev_name = NULL, *dev_uuid = NULL, *capacity_str = NULL;
+	char inactive_str[] = "inactive_table_hash=";
+	unsigned int inactive_len = strlen(inactive_str);
+	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 error1;
+
+	if (md->ima.inactive_table.device_metadata_len &&
+	    md->ima.inactive_table.hash_len) {
+		memcpy(device_table_data + l, md->ima.inactive_table.device_metadata,
+		       md->ima.inactive_table.device_metadata_len);
+		l += md->ima.inactive_table.device_metadata_len;
+
+		memcpy(device_table_data + l, inactive_str, inactive_len);
+		l += inactive_len;
+
+		memcpy(device_table_data + l, md->ima.inactive_table.hash,
+			   md->ima.inactive_table.hash_len);
+
+		l += md->ima.inactive_table.hash_len;
+
+		memcpy(device_table_data + l, ";", 1);
+		l++;
+	}
+
+	if (!l) {
+		if (dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio))
+			goto error2;
+
+		scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
+			  "name=%s,uuid=%s;table_clear=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("table_clear", device_table_data, l, noio);
+
+	if (new_map) {
+		if (md->ima.inactive_table.hash &&
+		    md->ima.inactive_table.hash != md->ima.active_table.hash)
+			kfree(md->ima.inactive_table.hash);
+
+		md->ima.inactive_table.hash = NULL;
+		md->ima.inactive_table.hash_len = 0;
+
+		if (md->ima.inactive_table.device_metadata &&
+		    md->ima.inactive_table.device_metadata != md->ima.active_table.device_metadata)
+			kfree(md->ima.inactive_table.device_metadata);
+
+		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.hash) {
+			md->ima.inactive_table.hash = md->ima.active_table.hash;
+			md->ima.inactive_table.hash_len = md->ima.active_table.hash_len;
+		}
+
+		if (md->ima.active_table.device_metadata) {
+			md->ima.inactive_table.device_metadata =
+				md->ima.active_table.device_metadata;
+			md->ima.inactive_table.device_metadata_len =
+				md->ima.active_table.device_metadata_len;
+			md->ima.inactive_table.num_targets =
+				md->ima.active_table.num_targets;
+		}
+	}
+
+	kfree(dev_name);
+	kfree(dev_uuid);
+error2:
+	kfree(capacity_str);
+error1:
+	kfree(device_table_data);
+}

drivers/md/dm-ima.h

@@ -51,6 +51,7 @@ 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);
 void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all);
+void dm_ima_measure_on_table_clear(struct mapped_device *md, bool new_map);
 
 #else
 
@@ -58,6 +59,7 @@ 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) {}
 static inline void dm_ima_measure_on_device_remove(struct mapped_device *md, bool remove_all) {}
+static inline void dm_ima_measure_on_table_clear(struct mapped_device *md, bool new_map) {}
 
 #endif /* CONFIG_IMA */
 

drivers/md/dm-ioctl.c

@@ -1505,6 +1505,7 @@ static int table_clear(struct file *filp, struct dm_ioctl *param, size_t param_s
 	struct hash_cell *hc;
 	struct mapped_device *md;
 	struct dm_table *old_map = NULL;
+	bool has_new_map = false;
 
 	down_write(&_hash_lock);
 
@@ -1518,6 +1519,7 @@ static int table_clear(struct file *filp, struct dm_ioctl *param, size_t param_s
 	if (hc->new_map) {
 		old_map = hc->new_map;
 		hc->new_map = NULL;
+		has_new_map = true;
 	}
 
 	param->flags &= ~DM_INACTIVE_PRESENT_FLAG;
@@ -1529,6 +1531,7 @@ static int table_clear(struct file *filp, struct dm_ioctl *param, size_t param_s
 		dm_sync_table(md);
 		dm_table_destroy(old_map);
 	}
+	dm_ima_measure_on_table_clear(md, has_new_map);
 	dm_put(md);
 
 	return 0;