Description

The assign function casts a reference to a const ptr and then to a mut ptr, before writing to it.

#[inline(always)]
pub unsafe fn assign(&self, new_owner: &Pubkey) {
    #[allow(invalid_reference_casting)]
    core::ptr::write_volatile(&(*self.raw).owner as *const _ as *mut Pubkey, *new_owner);
}

Casting an immutable reference & to a mutable one &mut, or a mut ptr, is always undefined behavior, as pointed out by the Rustonomicon↗. Here the #[allow(invalid_reference_casting)] attribute is used to silence the error the compiler throws otherwise, indicating the undefined behavior.

Impact

This may lead to undefined behavior resulting from casting an immutable reference to a mutable pointer.

Recommendations

Avoid taking an immutable reference, and directly cast a mutable reference to the mutable pointer first. Additionally, consider using core::ptr::write(..) over write_volatile as there is no direct need for a volatile write.

Remediation