[PATCH v2 07/10] dm-ima: Fix issues with dm_ima_measure_on_device_rename

[Benjamin Marzinski <bmarzins@redhat.com>]

dm_ima_measure_on_device_rename() can be called on a device before it
ever loads a table, so it needs to handle the case where there is no
table metadata. Also, it was only updating the table_metadata on the
active table. If there was an inactive table when the device was renamed
and that table was later swapped in as the active table, it would
still have the old name. dm_ima_measure_on_device_rename() was also
needlessly allocating new memory for the updated table metadata, instead
of just reusing the existing memory.

Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com>
---
 drivers/md/dm-ima.c | 69 ++++++++++++++++++++++++---------------------
 1 file changed, 37 insertions(+), 32 deletions(-)

diff --git a/drivers/md/dm-ima.c b/drivers/md/dm-ima.c
index 75c46b5af3f7..f563c4381489 100644
--- a/drivers/md/dm-ima.c
+++ b/drivers/md/dm-ima.c
@@ -133,22 +133,18 @@ void dm_ima_context_table_op(struct mapped_device *md,
 }
 
 /*
- * Internal function to allocate and copy device data for IMA measurements.
+ * Internal function to copy device data for IMA measurements.
  */
-static int dm_ima_alloc_and_copy_device_data(struct mapped_device *md, char **device_data,
-					     struct dm_ima_context *context,
-					     unsigned int num_targets, bool noio)
+static void dm_ima_copy_device_data(struct mapped_device *md, char *device_data,
+				    struct dm_ima_context *context,
+				    unsigned int num_targets)
 {
-	*device_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN, noio);
-	if (!(*device_data))
-		return -ENOMEM;
-
-	scnprintf(*device_data, DM_IMA_DEVICE_BUF_LEN,
+	memset(device_data, 0, DM_IMA_DEVICE_BUF_LEN);
+	scnprintf(device_data, DM_IMA_DEVICE_BUF_LEN,
 		  "name=%s,uuid=%s,major=%d,minor=%d,minor_count=%d,num_targets=%u;",
 		  context->dev_name, context->dev_uuid, md->disk->major,
 		  md->disk->first_minor, md->disk->minors, num_targets);
 
-	return 0;
 }
 
 /*
@@ -223,11 +219,14 @@ void dm_ima_measure_on_table_load(struct dm_table *table,
 
 	num_targets = table->num_targets;
 
-	fix_context_strings(context);
-	if (dm_ima_alloc_and_copy_device_data(table->md, &device_data_buf,
-					      context, num_targets, noio))
+	device_data_buf = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN, noio);
+	if (!device_data_buf)
 		goto error;
 
+	fix_context_strings(context);
+	dm_ima_copy_device_data(table->md, device_data_buf, context,
+				num_targets);
+
 	sha256_init(&hash_ctx);
 
 	memcpy(ima_buf + l, DM_IMA_VERSION_STR, strlen(DM_IMA_VERSION_STR));
@@ -626,48 +625,54 @@ void dm_ima_measure_on_table_clear(struct mapped_device *md,
 void dm_ima_measure_on_device_rename(struct mapped_device *md,
 				     struct dm_ima_context *context)
 {
-	char *old_device_data = NULL, *new_device_data = NULL;
+	char *old_device_data = NULL;
 	char *combined_device_data = NULL, *capacity_str = NULL;
 	bool noio = true;
 	int len;
+	struct dm_ima_device_table_metadata *table;
 
 	if (unlikely(!context))
 		return;
 
 	wait_to_measure(&md->ima, context->update_idx);
 
-	fix_context_strings(context);
-	if (dm_ima_alloc_and_copy_device_data(md, &new_device_data, context,
-					      md->ima.active_table.num_targets,
-					      noio))
-		goto error;
-
 	combined_device_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN * 2, noio);
 	if (!combined_device_data)
-		goto error;
+		goto exit;
 
 	if (dm_ima_alloc_and_copy_capacity_str(md, &capacity_str, noio) < 0)
-		goto error;
-
-	old_device_data = md->ima.active_table.device_metadata;
-
-	md->ima.active_table.device_metadata = new_device_data;
-	md->ima.active_table.device_metadata_len = strlen(new_device_data);
+		goto exit;
 
+	if (md->ima.active_table.device_metadata)
+		old_device_data = md->ima.active_table.device_metadata;
+	else if (md->ima.inactive_table.device_metadata)
+		old_device_data = md->ima.inactive_table.device_metadata;
+	else
+		old_device_data = "device_rename=no_data;";
+	fix_context_strings(context);
 	len = scnprintf(combined_device_data, DM_IMA_DEVICE_BUF_LEN * 2,
 			"%s%snew_name=%s,new_uuid=%s;%s", DM_IMA_VERSION_STR, old_device_data,
 			context->dev_name, context->dev_uuid, capacity_str);
 
-	dm_ima_measure_data("dm_device_rename", combined_device_data, len, noio);
+	if (md->ima.active_table.device_metadata) {
+		table = &md->ima.active_table;
+		dm_ima_copy_device_data(md, table->device_metadata, context,
+					table->num_targets);
+		table->device_metadata_len = strlen(table->device_metadata);
+	}
 
-	goto exit;
+	if (md->ima.inactive_table.device_metadata) {
+		table = &md->ima.inactive_table;
+		dm_ima_copy_device_data(md, table->device_metadata, context,
+					table->num_targets);
+		table->device_metadata_len = strlen(table->device_metadata);
+	}
+
+	dm_ima_measure_data("dm_device_rename", combined_device_data, len, noio);
 
-error:
-	kfree(new_device_data);
 exit:
 	kfree(capacity_str);
 	kfree(combined_device_data);
-	kfree(old_device_data);
 
 	wake_next_measure(&md->ima);
 }
-- 
2.53.0