dynamicstream: add area before add path #3998
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Summary of ChangesHello @3AceShowHand, I'm Gemini Code Assist1! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed! This pull request refactors the Highlights
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Code Review
This pull request refactors the dynstream API to separate area management from path management by introducing AddArea and RemoveArea methods, and updating AddPath. This is a good design improvement that makes the API cleaner.
However, I've found a critical issue in the implementation of memory_control.go where pointers to stack variables are stored, which can lead to memory corruption. I've left detailed comments on how to fix this.
Additionally, I've pointed out a minor inefficiency in subscription_client.go where AddArea is called redundantly.
Please address the critical issue before merging.
| func (m *memControl[A, P, T, D, H]) addArea(area A, settings AreaSettings) { | ||
| settings.fix() | ||
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| m.mutex.Lock() | ||
| defer m.mutex.Unlock() | ||
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| m.areaSettingsMap[area] = settings | ||
| if as, ok := m.areaStatMap[area]; ok { | ||
| as.settings.Store(&settings) | ||
| } | ||
| } |
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The settings parameter is passed by value, so it's a local copy on the stack. Storing its address with as.settings.Store(&settings) on line 318 is incorrect as the pointer will be invalid after addArea returns. This can lead to memory corruption.
You should allocate settings on the heap before storing a pointer to it. For example:
if as, ok := m.areaStatMap[area]; ok {
// The `settings` is a copy on the stack, we can't store a pointer to it.
// So we need to allocate a new one on the heap.
s := new(AreaSettings)
*s = settings
as.settings.Store(s)
}| func (m *memControl[A, P, T, D, H]) addPathToArea(path *pathInfo[A, P, T, D, H], feedbackChan chan<- Feedback[A, P, D]) { | ||
| m.mutex.Lock() | ||
| defer m.mutex.Unlock() | ||
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| area, ok := m.areaStatMap[path.area] | ||
| areaStat, ok := m.areaStatMap[path.area] | ||
| if !ok { | ||
| area = newAreaMemStat(path.area, m, settings, feedbackChan) | ||
| m.areaStatMap[path.area] = area | ||
| settings, ok := m.areaSettingsMap[path.area] | ||
| if !ok { | ||
| settings = AreaSettings{} | ||
| } | ||
| settings.fix() | ||
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| areaStat = newAreaMemStat(path.area, m, settings, feedbackChan) | ||
| m.areaStatMap[path.area] = areaStat | ||
| } else if settings, ok := m.areaSettingsMap[path.area]; ok { | ||
| // Ensure the stat uses the latest settings from AddArea. | ||
| settings.fix() | ||
| areaStat.settings.Store(&settings) | ||
| } | ||
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| path.areaMemStat = area | ||
| area.pathMap.Store(path.path, path) | ||
| area.pathCount.Add(1) | ||
| // Update the settings | ||
| area.settings.Store(&settings) | ||
| path.areaMemStat = areaStat | ||
| areaStat.pathMap.Store(path.path, path) | ||
| areaStat.pathCount.Add(1) | ||
| } |
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This function has a critical bug related to storing pointers to stack variables, which can lead to memory corruption.
- On line 357,
areaStat.settings.Store(&settings)stores a pointer tosettings, which is a local variable (a copy from the map). This pointer becomes invalid whenaddPathToAreareturns. - On line 352,
newAreaMemStatis called withsettings, which is also a local variable. ThenewAreaMemStatfunction also stores a pointer to itssettingsparameter, which is a copy on its own stack. This is also a bug.
To fix this, you need to ensure you are storing pointers to heap-allocated AreaSettings objects. For example, by using new(AreaSettings) before storing the pointer.
| s.ds.AddArea(0, areaSetting) | ||
| s.ds.AddPath(rt.subID, rt) |
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The AddArea call is made for every subscription, but since the area is always 0 and the settings are the same, this is redundant. This will repeatedly overwrite the settings for area 0.
It would be cleaner to call AddArea once when the subscriptionClient is initialized, for example in NewSubscriptionClient, and remove this call from the Subscribe method.
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What problem does this PR solve?
Issue Number: close #xxx
What is changed and how it works?
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Tests
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Will it cause performance regression or break compatibility?
Do you need to update user documentation, design documentation or monitoring documentation?
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