Submitted by Zubat, also found by Femboys and n4nika
https://github.com/code-423n4/2024-07-optimism/blob/70556044e5e080930f686c4e5acde420104bb2c4/packages/contracts-bedrock/src/dispute/FaultDisputeGame.sol#L883-L895
Suppose we have a situation where the MIPS geth goes wrong and always panics. The vmStatus can only be either UNFINISHED or PANIC.
In the current execution bisection game system, the UNFINISHED state can not be used as the root claim; the PANIC state can always be attacked. So we can counter every bisection game at SPLIT_DEPTH + 1; none of the claims at SPLIT_DEPTH are challenged. Inductively, claims agreeing with SPLIT_DEPTH are not challengable.
In the current configuration, SPLIT_DEPTH is set to 30, so we can deny any dispute against the root claim at depth 0. If that were to happen, the state of the L2 output root could be hijacked and unrecoverable.
Its unclear if there are easy methods to trigger panic in the MIPS VM.
One possible way is to leverage the privilege, as the batcher is currently controlled by a centralized trusted entity. Ordinary users cannot construct the batches and channels for the rollup, but the batcher can freely set the payload blob to L1.
https://github.com/code-423n4/2024-07-optimism/blob/main/op-node/rollup/derive/channel.go#L169-L205
A malicious batcher could compress a huge amount of zero blobs, upload them to L1, and force the MIPS VM to decompress them. Considering the limited memory resources of the MIPS VM and the absence of garbage collection in the MIPS go-ethereum, the VM could be very easily corrupted.
Set the split_depth to an odd number.
DoS
Inphi (Optimism) confirmed and commented:
