From fe7f3a6f26a1e9fc14e97d98d8db1aa07819861d Mon Sep 17 00:00:00 2001
From: "Admiral H. Curtiss" <pikachu025@gmail.com>
Date: Fri, 22 Oct 2021 06:27:37 +0200
Subject: [PATCH] RiivolutionPatcher: Protect against three or more dots in
 path traversal.

---
 Source/Core/DiscIO/RiivolutionPatcher.cpp | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/Source/Core/DiscIO/RiivolutionPatcher.cpp b/Source/Core/DiscIO/RiivolutionPatcher.cpp
index 8f1b88caf3..2e400507e1 100644
--- a/Source/Core/DiscIO/RiivolutionPatcher.cpp
+++ b/Source/Core/DiscIO/RiivolutionPatcher.cpp
@@ -98,6 +98,13 @@ FileDataLoaderHostFS::MakeAbsoluteFromRelative(std::string_view external_relativ
         result.pop_back();
       result.pop_back();
     }
+    else if (std::all_of(element.begin(), element.end(), [](char c) { return c == '.'; }))
+    {
+      // This is a triple, quadruple, etc. dot.
+      // Some file systems treat this as several 'up' path traversals, but Riivolution does not.
+      // If someone tries this just error out, it wouldn't work sensibly in Riivolution anyway.
+      return std::nullopt;
+    }
     else
     {
       // We're going down a level.