[bug] Make RefundGas safer (potential issue)

[Unique-Divine]

The Ask

Deadline: 2024-10-15

• Inspect and verify the behavior of RefundGas with its own tests.
• It should not be possible to refund negative gas
• RefundGas with 0 should be a no-op

Warning Generated by Coderabbit

[Click to Expand]

Prevent negative gas refund calculation

The calculation msg.Gas() - evmResp.GasUsed could result in a negative value if evmResp.GasUsed exceeds msg.Gas(). This could lead to unintended behavior or panic due to negative gas values.

Consider ensuring the refund amount is non-negative:

+refundGas := msg.Gas() - evmResp.GasUsed
+if refundGas < 0 {
+    refundGas = 0
+}
 if err = k.RefundGas(ctx, msg, refundGas, evmConfig.Params.EvmDenom); err != nil {
     return nil, errors.Wrapf(err, "failed to refund leftover gas to sender %s", msg.From())
 }

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

	refundGas := msg.Gas() - evmResp.GasUsed
	if refundGas < 0 {
		refundGas = 0
	}
	if err = k.RefundGas(ctx, msg, refundGas, evmConfig.Params.EvmDenom); err != nil {
		return nil, errors.Wrapf(err, "failed to refund leftover gas to sender %s", msg.From())
	}

Originally posted by @coderabbitai[bot] in #2053 (comment)