CVE-2026-99273: ksmbd: reserve space for the UTF-16 terminator in stream info

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: reserve space for the UTF-16 terminator in stream info

smbstrtoUTF16() always writes a terminating zero UTF-16 unit after the converted characters, but getfilestreaminfo() budgets only sizeof(struct smb2filestreaminfo) + streamlen 2 for a stream entry and sizeof(struct smb2filestreaminfo) + 7 2 for the trailing "::$DATA" entry. When an entry exactly fills the 448-byte small response buffer, the terminator is written two bytes past the allocation.

Reserve one extra UTF-16 unit in both budget checks. The terminator is not part of the wire format, so the reported lengths are unchanged.