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core/vm: fix overflow in gas calculation formula

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This commit is contained in:
Martin Holst Swende 2017-06-28 09:51:31 +02:00
parent 9e5f03b6c4
commit bae7565231
1 changed files with 10 additions and 6 deletions
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16
core/vm/gas_table.go
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@ -17,7 +17,6 @@
package vm
import (
gmath "math"
"math/big"
"github.com/ethereum/go-ethereum/common"
@ -28,15 +27,20 @@ import (
// memoryGasCosts calculates the quadratic gas for memory expansion. It does so
// only for the memory region that is expanded, not the total memory.
func memoryGasCost(mem *Memory, newMemSize uint64) (uint64, error) {
// The maximum that will fit in a uint64 is max_word_count - 1
// anything above that will result in an overflow.
if newMemSize > gmath.MaxUint64-32 {
return 0, errGasUintOverflow
}
if newMemSize == 0 {
return 0, nil
}
// The maximum that will fit in a uint64 is max_word_count - 1
// anything above that will result in an overflow.
// Additionally, a newMemSize which results in a
// newMemSizeWords larger than 0x7ffffffff will cause the square operation
// to overflow.
// The constant 0xffffffffe0 is the highest number that can be used without
// overflowing the gas calculation
if newMemSize > 0xffffffffe0 {
return 0, errGasUintOverflow
}
newMemSizeWords := toWordSize(newMemSize)
newMemSize = newMemSizeWords * 32