File 648f763e-Fix-memory-corruption-on-error-in-parse_selector_sch.patch of Package libsass.7438

From 648f763ede97f9a2c2c843a0a18ac18bbde3507b Mon Sep 17 00:00:00 2001
From: Marcel Greter <marcel.greter@ocbnet.ch>
Date: Fri, 6 Oct 2017 18:44:25 +0200
Subject: [PATCH] Fix memory corruption on error in parse_selector_schema

---
 src/eval.cpp | 19 ++++++++++++++++++-
 src/file.cpp |  2 +-
 2 files changed, 19 insertions(+), 2 deletions(-)

Index: libsass-3.3.2/src/eval.cpp
===================================================================
--- libsass-3.3.2.orig/src/eval.cpp
+++ libsass-3.3.2/src/eval.cpp
@@ -1513,8 +1513,28 @@ namespace Sass {
     // the parser will look for a brace to end the selector
     std::string result_str(s->contents()->perform(this)->perform(&to_string));
     result_str = unquote(Util::rtrim(result_str)) + "{";
-    Parser p = Parser::from_c_str(result_str.c_str(), ctx, s->pstate());
-    return operator()(p.parse_selector_list(exp.block_stack.back()->is_root()));
+    char* temp_cstr = sass_copy_c_string(result_str.c_str());
+    ctx.strings.push_back(temp_cstr); // attach to context
+    Parser p = Parser::from_c_str(temp_cstr, ctx, s->pstate());
+    p.last_media_block = s->media_block();
+    bool root = exp.block_stack.back()->is_root();
+    Selector_List* sl = p.parse_selector_list(root);
+    auto vec_str_rend = ctx.strings.rend();
+    auto vec_str_rbegin = ctx.strings.rbegin();
+    // remove the first item searching from the back
+    // we cannot assume our item is still the last one
+    // order is not important, so we can optimize this
+    auto it = std::find(vec_str_rbegin, vec_str_rend, temp_cstr);
+    // undefined behavior if not found!
+    if (it != vec_str_rend) {
+      // overwrite with last item
+      *it = ctx.strings.back();
+      // remove last one from vector
+      ctx.strings.pop_back();
+      // free temporary copy
+      free(temp_cstr);
+    }
+    return operator()(sl);
   }
 
   Expression* Eval::operator()(Parent_Selector* p)