advapi32: Fix rewinding the last path segment in SetSecurityInfo().

In particular, handle the case where an object has no name. In theory, this should not happen for regular files, but SetSecurityInfo() is almost certainly not supposed to care about that [i.e. this code probably belongs in the server, at the very least]. However, fixing that will require much more work. While we're at it, rewrite the code to be a little more idiomatic about its intent.

advapi32: Fix rewinding the last path segment in SetSecurityInfo().
c05973d0 · Zebediah Figura · Alexandre Julliard · 3ecedb7e · c05973d0
Commit c05973d0 authored Oct 14, 2023 by Zebediah Figura Committed by Alexandre Julliard Oct 16, 2023
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security.c dlls/advapi32/security.c +5 -4

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--- a/dlls/advapi32/security.c
+++ b/dlls/advapi32/security.c
@@ -2969,10 +2969,11 @@ DWORD WINAPI SetSecurityInfo(HANDLE handle, SE_OBJECT_TYPE ObjectType,
                    return RtlNtStatusToDosError(status);
                }

-                for (name_info->Name.Length-=2; name_info->Name.Length>0; name_info->Name.Length-=2)
-                    if (name_info->Name.Buffer[name_info->Name.Length/2-1]=='\\' ||
-                            name_info->Name.Buffer[name_info->Name.Length/2-1]=='/')
-                        break;
+                if (name_info->Name.Length && name_info->Name.Buffer[(name_info->Name.Length / 2) - 1] == '\\')
+                    name_info->Name.Length -= 2;
+                while (name_info->Name.Length && name_info->Name.Buffer[(name_info->Name.Length / 2) - 1] != '\\')
+                    name_info->Name.Length -= 2;
+
                if (name_info->Name.Length)
                {
                    OBJECT_ATTRIBUTES attr;