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Merge pull request #13516 from ethereum/fix-yul-interpreter-memory-access

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Fix memory expansion semantics in the yul interpreter.
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Daniel 2022-12-01 15:42:41 +01:00 committed by GitHub
commit 851cc09742
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3 changed files with 37 additions and 7 deletions
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10
test/libyul/yulInterpreterTests/zero_range.yul Normal file
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@ -0,0 +1,10 @@
{
calldatacopy(32, 0, 0)
// Used to store 32
sstore(0, msize())
}
// ----
// Trace:
// CALLDATACOPY(32, 0, 0)
// Memory dump:
// Storage dump:

19
test/tools/yulInterpreter/EVMInstructionInterpreter.cpp
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@ -499,13 +499,15 @@ u256 EVMInstructionInterpreter::evalBuiltin(
bool EVMInstructionInterpreter::accessMemory(u256 const& _offset, u256 const& _size)
{
if (((_offset + _size) >= _offset) && ((_offset + _size + 0x1f) >= (_offset + _size)))
if (_size == 0)
return true;
else if (((_offset + _size) >= _offset) && ((_offset + _size + 0x1f) >= (_offset + _size)))
{
u256 newSize = (_offset + _size + 0x1f) & ~u256(0x1f);
m_state.msize = max(m_state.msize, newSize);
// We only record accesses to contiguous memory chunks that are at most 0xffff bytes
// in size and at an offset of at most numeric_limits<size_t>::max() - 0xffff
return _size <= 0xffff && _offset <= u256(numeric_limits<size_t>::max() - 0xffff);
// We only record accesses to contiguous memory chunks that are at most s_maxRangeSize bytes
// in size and at an offset of at most numeric_limits<size_t>::max() - s_maxRangeSize
return _size <= s_maxRangeSize && _offset <= u256(numeric_limits<size_t>::max() - s_maxRangeSize);
}
else
m_state.msize = u256(-1);
@ -513,6 +515,15 @@ bool EVMInstructionInterpreter::accessMemory(u256 const& _offset, u256 const& _s
return false;
}
bytes EVMInstructionInterpreter::readMemory(u256 const& _offset, u256 const& _size)
{
yulAssert(_size <= s_maxRangeSize, "Too large read.");
bytes data(size_t(_size), uint8_t(0));
for (size_t i = 0; i < data.size(); ++i)
data[i] = m_state.memory[_offset + i];
return data;
}
u256 EVMInstructionInterpreter::readMemoryWord(u256 const& _offset)
{
return u256(h256(m_state.readMemory(_offset, 32)));

15
test/tools/yulInterpreter/EVMInstructionInterpreter.h
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@ -88,9 +88,15 @@ public:
);
private:
/// Checks if the memory access is not too large for the interpreter and adjusts
/// msize accordingly.
/// @returns false if the amount of bytes read is lager than 0xffff
/// Checks if the memory access is valid and adjusts msize accordingly.
/// @returns true if memory access is valid, false otherwise
/// A valid memory access must satisfy all of the following pre-requisites:
/// - Sum of @param _offset and @param _size do not overflow modulo u256
/// - Sum of @param _offset, @param _size, and 31 do not overflow modulo u256 (see note below)
/// - @param _size is lesser than or equal to @a s_maxRangeSize
/// - @param _offset is lesser than or equal to the difference of numeric_limits<size_t>::max()
/// and @a s_maxRangeSize
/// Note: Memory expansion is carried out in multiples of 32 bytes.
bool accessMemory(u256 const& _offset, u256 const& _size = 32);
/// @returns the memory contents at the provided address.
/// Does not adjust msize, use @a accessMemory for that
@ -125,6 +131,9 @@ private:
InterpreterState& m_state;
/// Flag to disable trace of instructions that write to memory.
bool m_disableMemoryWriteInstructions;
public:
/// Maximum length for range-based memory access operations.
static constexpr unsigned s_maxRangeSize = 0xffff;
};
} // solidity::yul::test