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x/net: data race in trace package #60619

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ash2k opened this issue Jun 6, 2023 · 2 comments
Open

x/net: data race in trace package #60619

ash2k opened this issue Jun 6, 2023 · 2 comments
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NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one.
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@ash2k
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ash2k commented Jun 6, 2023

From https://github.com/golang/net/blob/10cf388024ca83e11a073bb365ccda2b2806d103/trace/events.go#L61-L66:

	data.Families = make([]string, 0, len(families))
	famMu.RLock()
	for name := range families {
		data.Families = append(data.Families, name)
	}
	famMu.RUnlock()

Shouldn't len(families) be done with the mutex held? It's a package-level field that seem to be protected by the mutex.

@gopherbot gopherbot added this to the Unreleased milestone Jun 6, 2023
@Nasfame
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Nasfame commented Jun 6, 2023

Concurrent safe implementation would be

        famMu.RLock()
	data.Families = make([]string, 0, len(families))
	for name := range families {
		data.Families = append(data.Families, name)
	}
	famMu.RUnlock()

Fix - to reduce unnecessary reallocations due to dirty reads

@dr2chase
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dr2chase commented Jun 6, 2023

@neild @ianlancetaylor

I don't think this is necessarily an issue, if the pre-allocation merely has to be mostly-right, since append will grow the slice if the capacity is too small.

@dr2chase dr2chase added the NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. label Jun 6, 2023
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