[PATCH 42/42] libmultipath: dm_addmap(): refuse creating map with empty WWID

[mwilck@suse.com]

From: Martin Wilck <mwilck@suse.com>

We already avoid creating maps with empty WWID in coalesce_paths()
as well as in ev_add_path(). The only code path where it's difficult
to prove (although extremely unlikely) that we can't call
dm_addmap(ACT_CREATE) with an empty WWID is update_path_groups()->
reload_map(). To make the code easier to review and avoid ugly
corner cases, simply refuse to create maps with a zero-length
WWID.

Signed-off-by: Martin Wilck <mwilck@suse.com>
---
 libmultipath/devmapper.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/libmultipath/devmapper.c b/libmultipath/devmapper.c
index a177a54..fb7675c 100644
--- a/libmultipath/devmapper.c
+++ b/libmultipath/devmapper.c
@@ -352,6 +352,12 @@ dm_addmap (int task, const char *target, struct multipath *mpp,
 	char *prefixed_uuid = NULL;
 	uint32_t cookie = 0;
 
+	if (task == DM_DEVICE_CREATE && strlen(mpp->wwid) == 0) {
+		condlog(1, "%s: refusing to create map with empty WWID",
+			mpp->alias);
+		return 0;
+	}
+
 	/* Need to add this here to allow 0 to be passed in udev_flags */
 	udev_flags |= DM_UDEV_DISABLE_LIBRARY_FALLBACK;
 
@@ -368,18 +374,16 @@ dm_addmap (int task, const char *target, struct multipath *mpp,
 		dm_task_set_ro(dmt);
 
 	if (task == DM_DEVICE_CREATE) {
-		if (strlen(mpp->wwid) > 0) {
-			prefixed_uuid = MALLOC(UUID_PREFIX_LEN +
-					       strlen(mpp->wwid) + 1);
-			if (!prefixed_uuid) {
-				condlog(0, "cannot create prefixed uuid : %s",
-					strerror(errno));
-				goto addout;
-			}
-			sprintf(prefixed_uuid, UUID_PREFIX "%s", mpp->wwid);
-			if (!dm_task_set_uuid(dmt, prefixed_uuid))
-				goto freeout;
+		prefixed_uuid = MALLOC(UUID_PREFIX_LEN +
+				       strlen(mpp->wwid) + 1);
+		if (!prefixed_uuid) {
+			condlog(0, "cannot create prefixed uuid : %s",
+				strerror(errno));
+			goto addout;
 		}
+		sprintf(prefixed_uuid, UUID_PREFIX "%s", mpp->wwid);
+		if (!dm_task_set_uuid(dmt, prefixed_uuid))
+			goto freeout;
 		dm_task_skip_lockfs(dmt);
 #ifdef LIBDM_API_FLUSH
 		dm_task_no_flush(dmt);
-- 
2.26.2