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Fix potential mem-leak from hotstuff #1514

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Oct 22, 2021
Merged

Fix potential mem-leak from hotstuff #1514

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f6218fa
fix potential mem-leak from hotstuff
zhangchiqing Oct 22, 2021
1b03335
Merge branch 'master' into leo/fix-potential-mem-leak-from-hotstuff
zhangchiqing Oct 22, 2021
288aaf0
Merge branch 'master' into leo/fix-potential-mem-leak-from-hotstuff
zhangchiqing Oct 22, 2021
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9 changes: 9 additions & 0 deletions consensus/hotstuff/voteaggregator/vote_aggregator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -153,6 +153,15 @@ func (va *VoteAggregator) StoreProposerVote(vote *model.Vote) bool {
return false
}
va.proposerVotes[vote.BlockID] = vote
// update viewToBlockIDSet
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We can't use updateState here, even though that will that also update the viewToBlockIDSet which is used for pruning.

The reason is that the proposer Vote might be invalid, which we don't want to update the state with.

However, the viewToBlockIDSet is safe to update alone, since it's purely used for pruning.

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proposer Vote might be invalid

Good observation. From the perspective of VoteAggregator, the proposer vote is still unchecked. A double voting attempt cannot be attributed without checking the vote first.

I was thinking that the EventHander always validates the proposer vote first:

flow-go/consensus/hotstuff/validator/validator.go

Line 86 in 5df7142

_, err := v.ValidateVote(proposal.ProposerVote(), block)

Nevertheless, this happens outside of the VoteAggregator and we should probably not rely on external components for critical validity checks.

blockIDSet, exists := va.viewToBlockIDSet[vote.View]
if exists {
blockIDSet[vote.BlockID] = struct{}{}
} else {
blockIDSet = make(map[flow.Identifier]struct{})
blockIDSet[vote.BlockID] = struct{}{}
va.viewToBlockIDSet[vote.View] = blockIDSet
}
return true
}

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21 changes: 21 additions & 0 deletions consensus/hotstuff/voteaggregator/vote_aggregator_test.go
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Expand Up @@ -835,6 +835,27 @@ func (as *AggregatorSuite) TestNonePruneAfterBlock() {
require.Equal(as.T(), 3, votingStatusLen)
}

// receive the block for view 2,3,4,5
// prune by view 5, should be all pruned
func (as *AggregatorSuite) TestPruneAll() {
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This test case was able to reproduce the issue. Without the fix, this test will fail

pruneView := uint64(5)
for i := 2; i <= 5; i++ {
view := uint64(i)
bp := newMockBlock(as, view, as.participants[i].NodeID)
as.aggregator.StoreProposerVote(bp.ProposerVote())
}

require.Len(as.T(), as.aggregator.proposerVotes, 4)

as.aggregator.PruneByView(pruneView)
// proposerVotes should be all pruned, otherwise, there is memory leak
require.Len(as.T(), as.aggregator.proposerVotes, 0)
require.Len(as.T(), as.aggregator.blockIDToVotingStatus, 0)
require.Len(as.T(), as.aggregator.createdQC, 0)
require.Len(as.T(), as.aggregator.viewToVoteID, 0)
require.Len(as.T(), as.aggregator.viewToBlockIDSet, 0)
}

// RANDOM BEACON
// if there are 7 nodes, it requires 4 votes for random beacon,
// and receives the block from proposer who has 80% stake,
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