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Fail double mapper creation when RLIMIT_FSIZE leaves no usable size #134526

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Fail double mapper creation when RLIMIT_FSIZE leaves no usable size #134526

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12 changes: 12 additions & 0 deletions src/coreclr/minipal/Unix/doublemapping.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -136,6 +136,18 @@ bool VMToOSInterface::CreateDoubleMemoryMapper(void** pHandle, size_t *pMaxExecu
}
#endif // RLIMIT_FSIZE

// The clipping above can leave nothing to map - RLIMIT_FSIZE of zero is the plain case,
// and it is a realistic one for a process that is not allowed to create files at all.
// A zero sized mapper cannot back a single executable allocation, so reporting success
// here only hides the problem from ExecutableAllocator::Initialize(), which already knows
// how to continue with W^X disabled when this function fails. Failing here instead lets
// the process run single mapped rather than fail to start.
if (maxDoubleMappedMemorySize == 0)
{
close(fd);
return false;
}

if (ftruncate(fd, maxDoubleMappedMemorySize) == -1)
{
close(fd);
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