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les/utils: protect against WeightedRandomSelect overflow #21839

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Merged
fjl merged 2 commits into from
Nov 23, 2020
Merged

les/utils: protect against WeightedRandomSelect overflow #21839

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9320bda
les/utils: protect WRS against sumWeight overflow
zsfelfoldi Nov 12, 2020
61350d0
les/flowcontrol: check BufLimit == 0
zsfelfoldi Nov 12, 2020
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4 changes: 4 additions & 0 deletions les/flowcontrol/control.go
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ package flowcontrol

import (
"fmt"
"math"
"sync"
"time"

Expand Down Expand Up @@ -316,6 +317,9 @@ func (node *ServerNode) CanSend(maxCost uint64) (time.Duration, float64) {
node.lock.RLock()
defer node.lock.RUnlock()

if node.params.BufLimit == 0 {
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@rjl493456442 rjl493456442 Nov 13, 2020

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So it's the root cause for overflowed stuff right? The bufferlimit is 0 but we don't have any protection.

return time.Duration(math.MaxInt64), 0
}
now := node.clock.Now()
node.recalcBLE(now)
maxCost += uint64(safetyMargin) * node.params.MinRecharge / uint64(fcTimeConst)
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11 changes: 11 additions & 0 deletions les/utils/weighted_select.go
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Expand Up @@ -17,7 +17,10 @@
package utils

import (
"math"
"math/rand"

"github.com/ethereum/go-ethereum/log"
)

type (
Expand Down Expand Up @@ -54,6 +57,14 @@ func (w *WeightedRandomSelect) IsEmpty() bool {

// setWeight sets an item's weight to a specific value (removes it if zero)
func (w *WeightedRandomSelect) setWeight(item WrsItem, weight uint64) {
if weight > math.MaxInt64-w.root.sumWeight {
// old weight is still included in sumWeight, remove and check again
w.setWeight(item, 0)
if weight > math.MaxInt64-w.root.sumWeight {
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@rjl493456442 rjl493456442 Nov 13, 2020

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Why we check the overflow twice?

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@rjl493456442 rjl493456442 Nov 13, 2020

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I see. For removing the old weight.

log.Error("WeightedRandomSelect overflow", "sumWeight", w.root.sumWeight, "new weight", weight)
weight = math.MaxInt64 - w.root.sumWeight
}
}
idx, ok := w.idx[item]
if ok {
w.root.setWeight(idx, weight)
Expand Down