GPG using sudo under another user, is `pinentry-mode loopback` safe?

There are 2 users: user1 and user2. When trying to use gpg via sudo *(symmetric decryption)*: user1@host: sudo -u user2 gpg /home/user2/pass.gpg an error gpg: decryption failed: No secret key. I set it to --pinentry-mode loopback and the password request happens (right in the terminal), I type and the decryption happens. Tell me, is this approach safe? I can't understand how this option works. The GnuPG website says: > Redirect Pinentry queries to the caller. This enables the use of > gpgme_set_passphrase_cb because pinentry queries are redirected to > gpgme.