dm ioctl: allow dm_copy_name_and_uuid to return only one field

Allow NULL buffer in dm_copy_name_and_uuid if you only want to return one of
the fields.

(Required by a following patch that adds these fields to sysfs.)

Signed-off-by: Milan Broz <mbroz@redhat.com>
Reviewed-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

1 files changed, 4 insertions, 2 deletions

diff --git a/drivers/md/dm-ioctl.c b/drivers/md/dm-ioctl.c
index 777c948180f9..8da7a017b4ef 100644
--- a/drivers/md/dm-ioctl.c
+++ b/drivers/md/dm-ioctl.c
@@ -1550,8 +1550,10 @@ int dm_copy_name_and_uuid(struct mapped_device *md, char *name, char *uuid)
                 goto out;
         }
 
-        strcpy(name, hc->name);
-        strcpy(uuid, hc->uuid ? : "");
+        if (name)
+                strcpy(name, hc->name);
+        if (uuid)
+                strcpy(uuid, hc->uuid ? : "");
 
 out:
         up_read(&_hash_lock);