winansi: check result and Buffer before using Name

NtQueryObject under Wine can return a success but fill out no name.
In those situations, Wine will set Buffer to NULL, and set result to
the sizeof(OBJECT_NAME_INFORMATION).

Running a command such as

echo "$(git.exe --version 2>/dev/null)"

will crash due to a NULL pointer dereference when the code attempts to
null terminate the buffer, although, weirdly, removing the subshell or
redirecting stdout to a file will not trigger the crash.

Code has been added to also check Buffer and Length to ensure the check
is as robust as possible due to the current behavior being fragile at
best, and could potentially change in the future

This code is based on the behavior of NtQueryObject under wine and
reactos.

Signed-off-by: Christopher Degawa <[email protected]>

Author: 1480c1

compat/winansi.c

@@ -573,6 +573,9 @@ static void detect_msys_tty(int fd)
 	if (!NT_SUCCESS(NtQueryObject(h, ObjectNameInformation,
 			buffer, sizeof(buffer) - 2, &result)))
 		return;
+	if (result < sizeof(*nameinfo) || !nameinfo->Name.Buffer ||
+		!nameinfo->Name.Length)
+		return;
 	name = nameinfo->Name.Buffer;
 	name[nameinfo->Name.Length / sizeof(*name)] = 0;