Fix integer overflow in analysis around gas cost of undefined instruction #93
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Codecov Report
@@ Coverage Diff @@
## master #93 +/- ##
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+ Coverage 94.89% 94.93% +0.03%
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Files 18 18
Lines 1801 1815 +14
Branches 182 184 +2
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+ Hits 1709 1723 +14
Misses 75 75
Partials 17 17 |
This was referenced Jul 16, 2019
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I found similar test in the |
Caused by integer overflow around undefined instruction's gas cost.
Prevent integer overflow when calculating block gas with undefined instructions.
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chfast
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axic
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Jul 17, 2019
| @@ -84,7 +84,8 @@ code_analysis analyze( | |||
| auto& instr = jumpdest ? analysis.instrs.back() : analysis.instrs.emplace_back(fns[c]); | |||
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| auto metrics = instr_table[c]; | |||
| block->gas_cost += metrics.gas_cost; | |||
| if (metrics.gas_cost > 0) // can be -1 for undefined instruction | |||
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If we know this instruction will be hit, shouldn't the cost be set to max instead (e.g. out of gas)?
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I think then it would stop with EVMC_OUT_OF_GAS at the beginning of the block, instead of expected EVMC_UNDEFINED_INSTRUCTION
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I believe we should set it to 0 as this is real gas cost of executing it. Setting it to "max" is a nice hack, but I don't waste 64-bits in the table just for it.
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Apr 27, 2021
Compile unittests and vmtests as C++11
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Without the fix it's not only UBSAN warning, but also the test fails, returning
EVMC_OUT_OF_GASinstead ofEVMC_UNDEFINED_INSTRUCTION.Overflow happens not at the place of fix but later during execution here
evmone/lib/evmone/instructions.cpp
Line 1164 in 47a1d47