sc/serviceability: error when resizing account in account_write: "Could not create program address with signer seeds: Provided seeds do not result in a valid address"

[snormore]

This issue was encountered in testnet last week when trying to update or delete links (context):

Could not create program address with signer seeds: Provided seeds do not result in a valid address

Coming from the invoke_signed call in account_write: https://github.com/malbeclabs/doublezero/blob/main/smartcontract/programs/doublezero-serviceability/src/helper.rs#L102-L115

invoke_signed(
    &system_instruction::transfer(payer_account.key, account.key, payment),
    &[
        account.clone(),
        payer_account.clone(),
        system_program.clone(),
    ],
    &[&[
        SEED_PREFIX,
        instance.seed(),
        &instance.index().to_le_bytes(),
        &[instance.bump_seed()],
    ]],
)?;

The resolution at the time was to temporarily hot patch a change to use invoke instead of invoke_signed, since we are transferring from the payer, so it doesn't really make sense that we're passing signer seed for the link account.

invoke(
    &system_instruction::transfer(payer_account.key, account.key, payment),
    &[
        account.clone(),
        payer_account.clone(),
        system_program.clone(),
    ],
)?;

It's unclear if this code path actually works, if it just works sometimes, or what's going on here, but the issue will likely come up again if not properly addressed.

[snormore]

cc @elitegreg @karl-dz @juan-malbeclabs

[juan-malbeclabs]

It’s odd that we’re just now noticing this as an error, given that it seems to have been used before. Your change sounds very reasonable.

[karl-dz]

Those signer seeds should have never been there. Like Juan says though, interesting that it hasn't come up before