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Fix FailFast message formatting race #56388

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Merged
merged 2 commits into from
Jul 27, 2021
Merged

Fix FailFast message formatting race #56388

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0865d76
Fix FailFast message formatting race
janvorli Jul 27, 2021
132f2c6
Fix the OOM case
janvorli Jul 27, 2021
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36 changes: 25 additions & 11 deletions src/coreclr/classlibnative/bcltype/system.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -195,6 +195,8 @@ INT32 QCALLTYPE SystemNative::GetProcessorCount()
// managed string object buffer. This buffer is not always used, see comments in
// the method below.
WCHAR g_szFailFastBuffer[256];
WCHAR *g_pFailFastBuffer = g_szFailFastBuffer;

#define FAIL_FAST_STATIC_BUFFER_LENGTH (sizeof(g_szFailFastBuffer) / sizeof(WCHAR))

// This is the common code for FailFast processing that is wrapped by the two
Expand Down Expand Up @@ -243,7 +245,7 @@ void SystemNative::GenericFailFast(STRINGREF refMesgString, EXCEPTIONREF refExce
// Another option would seem to be to implement a new frame type that
// protects object references as pinned, but that seems like overkill for
// just this problem.
WCHAR *pszMessage = NULL;
WCHAR *pszMessageBuffer = NULL;
DWORD cchMessage = (gc.refMesgString == NULL) ? 0 : gc.refMesgString->GetStringLength();

WCHAR * errorSourceString = NULL;
Expand All @@ -262,32 +264,44 @@ void SystemNative::GenericFailFast(STRINGREF refMesgString, EXCEPTIONREF refExce

if (cchMessage < FAIL_FAST_STATIC_BUFFER_LENGTH)
{
pszMessage = g_szFailFastBuffer;
// The static buffer can be used only once to avoid race condition with other threads
pszMessageBuffer = InterlockedExchangeT(&g_pFailFastBuffer, NULL);
}
else

if (pszMessageBuffer == NULL)
{
// We can fail here, but we can handle the fault.
CONTRACT_VIOLATION(FaultViolation);
pszMessage = new (nothrow) WCHAR[cchMessage + 1];
if (pszMessage == NULL)
pszMessageBuffer = new (nothrow) WCHAR[cchMessage + 1];
if (pszMessageBuffer == NULL)
{
// Truncate the message to what will fit in the static buffer.
cchMessage = FAIL_FAST_STATIC_BUFFER_LENGTH - 1;
pszMessage = g_szFailFastBuffer;
pszMessageBuffer = InterlockedExchangeT(&g_pFailFastBuffer, NULL);
}
}

if (cchMessage > 0)
memcpyNoGCRefs(pszMessage, gc.refMesgString->GetBuffer(), cchMessage * sizeof(WCHAR));
pszMessage[cchMessage] = W('\0');
const WCHAR *pszMessage;
if (pszMessageBuffer != NULL)
{
if (cchMessage > 0)
memcpyNoGCRefs(pszMessageBuffer, gc.refMesgString->GetBuffer(), cchMessage * sizeof(WCHAR));
pszMessageBuffer[cchMessage] = W('\0');
pszMessage = pszMessageBuffer;
}
else
{
pszMessage = W("There is not enough memory to print the supplied FailFast message.");
cchMessage = (DWORD)wcslen(pszMessage);
}

if (cchMessage == 0) {
WszOutputDebugString(W("CLR: Managed code called FailFast without specifying a reason.\r\n"));
}
else {
WszOutputDebugString(W("CLR: Managed code called FailFast, saying \""));
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Not your change, but to be consistent with the other CLR termination messages, this would be ...called FailFast. "));. They all suffix the message after a period.

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I suggest to keep it on one line (ie, space instead of \r\n). That is the existing pattern and it works well with logs and concurrent console output where the two lines can otherwise get separated.

WszOutputDebugString(W("CLR: Managed code called FailFast.\r\n"));
WszOutputDebugString(pszMessage);
WszOutputDebugString(W("\"\r\n"));
WszOutputDebugString(W("\r\n"));
}

LPCWSTR argExceptionString = NULL;
Expand Down