Failed Launch

[paradoxgoose]

I got forge installed, and it shows up in the launcher,but the game won't launch. it gives this error message:

Failed to start download.
Name: 1.12.2-forge-14.23.5.2854.jar
URL: https://launcher.mojang.com/v1/objects/0f275bc1547d01fa5f56ba34bdc87d981ee12daf/client.jar
Error details: Permission denied
Couldn't open file for download

and then the filename and path

and below that

Exists: Nonexistent

Also on one note, in the versions folder in .minecraft, there's a lock icon on the file.

I use Linux Ubuntu. Any idea what I can do?