EIP-170 related consensus error at Goerli block 5080941 #867
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This was referenced Oct 19, 2021
jlokier
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…ATA` This fixes #867 "EIP-170 related consensus error at Goerli block 5080941", and equivalent on other networks. There are some other EVM logic changes too: Refactored `writeContract`, how `RETURNDATA` is handled inside the EVM, and quirks before EIP-2 (Homestead). This fix allows sync to get past block 5080941 on Goerli, and probably equivalent on other networks. Here's a trace at batch 5080897..5081088: ``` TRC 2021-10-01 21:18:12.883+01:00 Persisting blocks file=persist_blocks.nim:43 fromBlock=5080897 toBlock=5081088 ... DBG 2021-10-01 21:18:13.270+01:00 Contract code size exceeds EIP170 topics="vm computation" file=computation.nim:236 limit=24577 actual=31411 DBG 2021-10-01 21:18:13.271+01:00 gasUsed neq cumulativeGasUsed file=process_block.nim:68 block=5080941/0A3537BC5BDFC637349E1C77D9648F2F65E2BF973ABF7956618F854B769DF626 gasUsed=3129669 cumulativeGasUsed=3132615 TRC 2021-10-01 21:18:13.271+01:00 peer disconnected file=blockchain_sync.nim:407 peer=<IP:PORT> ``` Although it says "Contract code size" and "gasUsed", this bug is more general than either contract size or gas. It's due to incorrect behaviour of EVM instructions `RETURNDATA` and `RETURNDATASIZE`. Sometimes when `writeContract` decides to reject writing the contract for any of several reasons (for example just insufficient gas), the unwritten contract code was being used as the "return data", and given to the caller. If the caller used `RETURNDATA` or `RETURNDATASIZE` ops, those incorrectly reported the contract code that didn't get written. EIP-211 (https://eips.ethereum.org/EIPS/eip-211) describes `RETURNDATA`: > "`CREATE` and `CREATE2` are considered to return the empty buffer in the > success case and the failure data in the failure case". The language is ambiguous. In fact "failure case" means when the contract uses `REVERT` to finish. It doesn't mean other failures like out of gas, EIP-170 limit, EIP-3541, etc. To be thorough, and to ensure we always do the right thing with real EVMC when that's finalised, this patch fixes the `RETURNDATA` issue in two places, either of which make Goerli block 5080941 pass. `writeContract` and how it is called are refactored to be clearer. It sets an error in the usual way if contract writing is rejected. (Anticipating EVMC where we'll use different error codes.) Also this has the change from @jangko 6548ff9 "fixes CREATE/CREATE2's `returndata` bug", making the caller EVM ignore any data except from `REVERT`. There are four behaviour changes: 1. On the callee side, it doesn't set `c.outputData` except for `REVERT`. 2. On the caller side, it doesn't read `child.outputData` except for `REVERT`. 3. There was a bug in processing before Homestead fork (EIP-2). We did not match the spec or other implementations; now we do. When there's insufficient gas, before Homestead it's treated as success but with an empty contract. https://github.com/ethereum/pyethereum/blob/d117c8f3fd93359fc641fd850fa799436f7c43b5/ethereum/processblock.py#L304 https://github.com/ethereum/go-ethereum/blob/401354976bb4/core/vm/instructions.go#L586 4. The Byzantium check has been removed, as it's unnecessary. Signed-off-by: Jamie Lokier <[email protected]>
jlokier
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This fixes #867 "EIP-170 related consensus error at Goerli block 5080941", and equivalent on other networks. This combines a change on the EVM-caller side with an EVM-side change from @jangko 6548ff9 "fixes CREATE/CREATE2's `returndata` bug", making the caller EVM ignore any data except from `REVERT`. Either change works by itself. The reason for both is to ensure we definitely comply with ambiguous EVMC expectations from either side of that boundary, and it makes the internal API clearer. As well as fixing a specific consensus issue, there are some other EVM logic changes too: Refactored `writeContract`, how `RETURNDATA` is handled inside the EVM, and changed behaviour with quirks before EIP-2 (Homestead). The fix allows sync to pass block 5080941 on Goerli, and probably equivalent on other networks. Here's a trace at batch 5080897..5081088: ``` TRC 2021-10-01 21:18:12.883+01:00 Persisting blocks file=persist_blocks.nim:43 fromBlock=5080897 toBlock=5081088 ... DBG 2021-10-01 21:18:13.270+01:00 Contract code size exceeds EIP170 topics="vm computation" file=computation.nim:236 limit=24577 actual=31411 DBG 2021-10-01 21:18:13.271+01:00 gasUsed neq cumulativeGasUsed file=process_block.nim:68 block=5080941/0A3537BC5BDFC637349E1C77D9648F2F65E2BF973ABF7956618F854B769DF626 gasUsed=3129669 cumulativeGasUsed=3132615 TRC 2021-10-01 21:18:13.271+01:00 peer disconnected file=blockchain_sync.nim:407 peer=<IP:PORT> ``` Although it says "Contract code size" and "gasUsed", this bug is more general than either contract size or gas. It's due to incorrect behaviour of EVM instructions `RETURNDATA` and `RETURNDATASIZE`. Sometimes when `writeContract` decides to reject writing the contract for any of several reasons (for example just insufficient gas), the unwritten contract code was being used as the "return data", and given to the caller. If the caller used `RETURNDATA` or `RETURNDATASIZE` ops, those incorrectly reported the contract code that didn't get written. EIP-211 (https://eips.ethereum.org/EIPS/eip-211) describes `RETURNDATA`: > "`CREATE` and `CREATE2` are considered to return the empty buffer in the > success case and the failure data in the failure case". The language is ambiguous. In fact "failure case" means when the contract uses `REVERT` to finish. It doesn't mean other failures like out of gas, EIP-170 limit, EIP-3541, etc. To be thorough, and to ensure we always do the right thing with real EVMC when that's finalised, this patch fixes the `RETURNDATA` issue in two places, either of which make Goerli block 5080941 pass. `writeContract` has been refactored to be caller, and so has where it's called. It sets an error in the usual way if contract writing is rejected -- that's anticipating EVMC, where we'll use different error codes later. Overall four behaviour changes: 1. On the callee side, it doesn't set `c.outputData` except for `REVERT`. 2. On the caller side, it doesn't read `child.outputData` except for `REVERT`. 3. There was a bug in processing before Homestead fork (EIP-2). We did not match the spec or other implementations; now we do. When there's insufficient gas, before Homestead it's treated as success but with an empty contract. https://github.com/ethereum/pyethereum/blob/d117c8f3fd93359fc641fd850fa799436f7c43b5/ethereum/processblock.py#L304 https://github.com/ethereum/go-ethereum/blob/401354976bb4/core/vm/instructions.go#L586 4. The Byzantium check has been removed, as it's unnecessary. Signed-off-by: Jamie Lokier <[email protected]>
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On Goerli, sync progress stops at block 5080941. After that point, trace output repeatedly shows
Contract code size exceeds EIP170andgasUsed neq cumulativeGasUsedmessages, and does not feed blocks to the database:This issue is already documented starting from Sync to Goerli #687 (comment). It's just copied here just to have its own issue, as there is more than one way to handle this.
It's consensus logic bug due to incorrect return data when a
CREATEorCREATE2operation try to make a contract larger than 24 kiB and the caller looks at theRETURNDATAorRETURNDATASIZE.The 24 kiB contract size limit is exceeded as early as block 4394113 (or 4394114, logs are ambiguous), but that's fine. The bug is in
RETURNDATA, and the first time that's checked is bblock 5080941.This issue is not related to London fork semantics. The fact it occurs for the first time in the London range (which starts at 5062605) is probably a coincidence.
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