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…NtCreateFile`. `CreateFileAtW` passes `NtCreateFile` a `UNICODE_STRING` built from an unterminated slice. That is valid, but Win32 paths (`RtlInitUnicodeString`, `RtlDosPathNameToNtPathName_U`) always leave a NUL right after the name, and some third-party endpoint-security products hook `NtCreateFile` and copy `ObjectName->Buffer` up to a NUL instead of `Length` bytes. With cap-std's directory-relative opens such a hook reads past the allocation, and the process crashes when the next page is inaccessible. We hit this in production on Windows machines with such a product installed, and carrying this change as a patch fixed it. Make `CreateFileAtW` take a NUL-terminated slice, with `Length` excluding the terminator and `MaximumLength` including it, as `RtlInitUnicodeString` does. `open_at`, its only caller, now appends the NUL once for both the `CreateFileW` and `CreateFileAtW` branches. The name the kernel sees is unchanged.
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CreateFileAtW passes to NtCreateFileCreateFileAtW passes to NtCreateFile.
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CreateFileAtWpassesNtCreateFileaUNICODE_STRINGbuilt from an unterminated slice. That is valid, but Win32 paths (RtlInitUnicodeString,RtlDosPathNameToNtPathName_U) always leave a NUL right after the name, and some third-party endpoint-security products hookNtCreateFileand copyObjectName->Bufferup to a NUL instead ofLengthbytes. With cap-std's directory-relative opens such a hook reads past the allocation, and the process crashes when the next page is inaccessible. We hit this in production on Windows machines with such a product installed, and carrying this change as a patch fixed it.Make
CreateFileAtWtake a NUL-terminated slice, withLengthexcluding the terminator andMaximumLengthincluding it, asRtlInitUnicodeStringdoes.open_at, its only caller, now appends the NUL once for both theCreateFileWandCreateFileAtWbranches. The name the kernel sees is unchanged.