8000 ✨ Add opt-in storage layout compatibility guard for UUPS by codermaybe · Pull Request #1500 · Vectorized/solady · GitHub
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✨ Add opt-in storage layout compatibility guard for UUPS #1500

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✨ Add opt-in storage layout compatibility guard for UUPS #1500

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@codermaybe codermaybe commented Nov 23, 2025

Description

Adds an optional storage layout compatibility check mechanism for UUPS upgrades to prevent storage collision vulnerabilities.

Changes

  • Added StorageLayoutMismatch() error to UUPSUpgradeable.sol
  • Added _checkStorageLayout(address newImplementation) virtual hook (empty by default for backwards compatibility)
  • Provided reference implementation in MockUUPSImplementation.sol using version hash comparison
  • Added test cases for both compatible and incompatible layout scenarios

Usage Pattern

Implementations can override _checkStorageLayout to enforce storage compatibility:

bytes32 private constant _STORAGE_LAYOUT_VERSION = keccak256("MyContract.v1");

function STORAGE_LAYOUT_VERSION() external pure returns (bytes32) {
    return _STORAGE_LAYOUT_VERSION;
}

function _checkStorageLayout(address newImpl) internal view override {
    // Check version hash matches - see MockUUPSImplementation.sol for full example
}

Design Decisions

  • Opt-in mechanism: Default empty implementation preserves existing behavior
  • Non-breaking: Zero impact on contracts that don't override the hook
  • Gas-optimized: Uses assembly for efficient staticcall and error handling
  • Flexible: Implementations can choose their own validation strategy

Addresses the storage layout safety concern raised in the original UUPS test demo.

Closes #1489

Checklist

Ensure you completed all of the steps below before submitting your pull request:

  • Ran forge fmt?
  • Ran forge test?

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UUPS upgrade: support checking slot conflicts

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