Fix rent exempt check

p-token/src/processor/shared/initialize_mint.rs

@@ -1,5 +1,4 @@
 use {
-    core::mem::size_of,
     pinocchio::{
         account_info::AccountInfo,
         program_error::ProgramError,
@@ -57,24 +56,24 @@ pub fn process_initialize_mint(
         (mint_info, None)
     };
 
-    // SAFETY: single mutable borrow to `mint_info` account data.
-    let mint = unsafe { load_mut_unchecked::<Mint>(mint_info.borrow_mut_data_unchecked())? };
-
-    if mint.is_initialized()? {
-        return Err(TokenError::AlreadyInUse.into());
-    }
-
-    // Check rent-exempt status of the mint account.
+    let mint_data_len = mint_info.data_len();
 
     let is_exempt = if let Some(rent_sysvar_info) = rent_sysvar_info {
         // SAFETY: single immutable borrow to `rent_sysvar_info`; account ID and length
         // are checked by `from_account_info_unchecked`.
         let rent = unsafe { Rent::from_account_info_unchecked(rent_sysvar_info)? };
-        rent.is_exempt(mint_info.lamports(), size_of::<Mint>())
+        rent.is_exempt(mint_info.lamports(), mint_data_len)
     } else {
-        Rent::get()?.is_exempt(mint_info.lamports(), size_of::<Mint>())
+        Rent::get()?.is_exempt(mint_info.lamports(), mint_data_len)
     };
 
+    // SAFETY: single mutable borrow to `mint_info` account data.
+    let mint = unsafe { load_mut_unchecked::<Mint>(mint_info.borrow_mut_data_unchecked())? };
+
+    if mint.is_initialized()? {
+        return Err(TokenError::AlreadyInUse.into());
+    }
+
     if !is_exempt {
         return Err(TokenError::NotRentExempt.into());
     }