diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 1502d664c892..58ffaede8d16 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -741,6 +741,8 @@ int btrfs_dev_replace_by_ioctl(struct btrfs_fs_info *fs_info,
 	if ((args->start.srcdevid == 0 && args->start.srcdev_name[0] == '\0') ||
 	    args->start.tgtdev_name[0] == '\0')
 		return -EINVAL;
+	args->start.srcdev_name[BTRFS_PATH_NAME_MAX] = 0;
+	args->start.tgtdev_name[BTRFS_PATH_NAME_MAX] = 0;
 
 	ret = btrfs_dev_replace_start(fs_info, args->start.tgtdev_name,
 					args->start.srcdevid,