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Validate addresses before calling DAC to avoid crashes on older runtimes #1380

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Merged
leculver merged 3 commits into from
Feb 24, 2026
+24 −1
Merged

Validate addresses before calling DAC to avoid crashes on older runtimes #1380

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a19bb44
Validate addresses before calling DAC to avoid crashes on older runtimes
leculver Feb 20, 2026
b091587
Update src/Microsoft.Diagnostics.Runtime/DacInterface/SosDac.cs
leculver Feb 21, 2026
2ec70a7
Add mt==0 guard to GetAssemblyLoadContext (crash #12 from dotnet/runt…
leculver Feb 22, 2026
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19 changes: 18 additions & 1 deletion src/Microsoft.Diagnostics.Runtime/DacInterface/SosDac.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -295,6 +295,12 @@ public string GetFrameName(ulong vtable)

public HResult GetFieldInfo(ulong mt, out MethodTableFieldInfo data)
{
if (mt == 0)
{
data = default;
return HResult.E_INVALIDARG;
}

return VTable.GetMethodTableFieldData(Self, mt, out data);
}

Expand Down Expand Up @@ -420,6 +426,11 @@ public HResult GetAppDomainData(ulong addr, out AppDomainData data)

public string? GetAppDomainName(ulong appDomain)
{
if (appDomain == 0)
{
return null;
}

return GetString(VTable.GetAppDomainName, appDomain);
}

Expand All @@ -436,7 +447,7 @@ public HResult GetAppDomainStoreData(out AppDomainStoreData data)
public HResult GetMethodTableData(ulong addr, out MethodTableData data)
{
// If the 2nd bit is set it means addr is actually a TypeHandle (which GetMethodTable does not support).
if ((addr & 2) == 2)
if (addr == 0 || (addr & 2) == 2)
{
data = default;
return HResult.E_INVALIDARG;
Expand Down Expand Up @@ -662,6 +673,9 @@ public enum ModuleMapTraverseKind

public HResult TraverseModuleMap(ModuleMapTraverseKind mt, ulong module, ModuleMapTraverse traverse)
{
if (module == 0)
return HResult.E_INVALIDARG;
Comment on lines +676 to +677
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Copilot AI Feb 20, 2026

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Inconsistent brace usage. According to .editorconfig line 275, braces are preferred (csharp_prefer_braces = true:warning). This simple return statement doesn't use braces, but GetFieldInfo (lines 298-302) uses braces for the same pattern. For consistency, consider either using braces here and in GetAppDomainName, or removing braces from GetFieldInfo.

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HResult hr = VTable.TraverseModuleMap(Self, mt, module, Marshal.GetFunctionPointerForDelegate(traverse), IntPtr.Zero);
GC.KeepAlive(traverse);
return hr;
Expand All @@ -688,6 +702,9 @@ public enum VCSHeapType

public HResult TraverseStubHeap(ulong heap, VCSHeapType type, LoaderHeapTraverse callback)
{
if (heap == 0)
return HResult.E_INVALIDARG;
Comment on lines +705 to +706
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Copilot AI Feb 20, 2026

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Inconsistent brace usage. According to .editorconfig line 275, braces are preferred (csharp_prefer_braces = true:warning). This simple return statement doesn't use braces, but GetFieldInfo (lines 298-302) uses braces for the same pattern. For consistency, consider either using braces here and in GetAppDomainName and TraverseModuleMap, or removing braces from GetFieldInfo.

Copilot uses AI. Check for mistakes.

HResult hr = VTable.TraverseVirtCallStubHeap(Self, heap, type, Marshal.GetFunctionPointerForDelegate(callback));
GC.KeepAlive(callback);
return hr;
Expand Down
6 changes: 6 additions & 0 deletions src/Microsoft.Diagnostics.Runtime/DacInterface/SosDac8.cs
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Expand Up @@ -24,6 +24,12 @@ public SOSDac8(DacLibrary library, IntPtr ptr)

public HResult GetAssemblyLoadContext(ClrDataAddress methodTable, out ClrDataAddress assemblyLoadContext)
{
if (methodTable == 0)
{
assemblyLoadContext = 0;
return HResult.E_INVALIDARG;
}

return VTable.GetAssemblyLoadContext(Self, methodTable, out assemblyLoadContext);
}

Expand Down