AccountInfo::assign is unsound

[brson]

Problem

Here's the definition:

    pub fn assign(&self, new_owner: &Pubkey) {
        // Set the non-mut owner field
        unsafe {
            std::ptr::write_volatile(
                self.owner as *const Pubkey as *mut [u8; 32],
                new_owner.to_bytes(),
            );
        }
    }

This is not allowed in Rust and causes undefined behavior. It's not clear what write_volatile is doing here, but it's probably not what is intended.

Proposed Solution

I don't see any way to do this without changing the definition of AccountInfo.

[jackcmay]

Right, we are not able to change AccountInfo, but is being replaced as part of the ABIv2 effort

#27384

[steveluscher]

Can this be closed as sufficiently covered by #27384, @Lichtso?

[Lichtso]

yes