Bug: STMRunner passes nil transaction bytes to deliverTx when estimate is false

[randy-cro]

Summary

In blockstm/txnrunner.go, STMRunner.Run fails to pass the raw transaction bytes to deliverTx when the estimate flag is false. This results in deliverTx being called with nil tx bytes, which will result in the transaction not executing in BaseApp.RunTx.

Affected Code

https://github.com/cosmos/cosmos-sdk/blob/main/blockstm/txnrunner.go#L66-L96

var (
    estimates []MultiLocations
    memTxs    [][]byte
)

if e.estimate {
    memTxs, estimates = preEstimates(txs, e.workers, authStore, bankStore, e.coinDenom(ms), e.txDecoder)
}

// ...inside ExecuteBlockWithEstimates callback:
var memTx []byte
if memTxs != nil {
    memTx = memTxs[txn]
}
results[txn] = deliverTx(memTx, msWrapper{ms}, int(txn), cache)

When estimate is false:

1. memTxs remains its zero value (nil)
2. if memTxs != nil check is false, so memTx stays nil
3. deliverTx(nil, ...) is called — the original txs[txn] bytes are never passed

Comparison with DefaultRunner

DefaultRunner correctly passes the raw transaction bytes:

https://github.com/cosmos/cosmos-sdk/blob/main/baseapp/txnrunner/default.go#L34

response = deliverTx(rawTx, nil, i, nil)

Suggested Fix

Fall back to the original txs[txn] when memTxs is nil or when the entry is nil:

var memTx []byte
if memTxs != nil && memTxs[txn] != nil {
    memTx = memTxs[txn]
} else {
    memTx = txs[txn]
}

This ensures raw transaction bytes are always passed to deliverTx, consistent with DefaultRunner behavior. It also handles the edge case where preEstimates skips a malformed transaction.

[linear]

SDK-458

[randy-cro]

Resolved in #25883