Limit number of symlinks that canonical() will resolve

	* src/filesystem/ops.cc (canonical): Simplify error handling and
	limit number of symlinks that can be resolved.

From-SVN: r228043

diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 578c5510b01c0d9e14c536437b226e6b7ac68e66..17d82e3de71ab4014c2838d008d66ef6231780a3 100644 (file)
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,3 +1,8 @@
+2015-09-23  Jonathan Wakely  <jwakely@redhat.com>
+
+       * src/filesystem/ops.cc (canonical): Simplify error handling and
+       limit number of symlinks that can be resolved.
+
 2015-09-23  Jonathan Wakely  <jwakely@redhat.com>
 
        * acinclude.m4 (GLIBCXX_CHECK_FILESYSTEM_DEPS): Remove _GLIBCXX_

diff --git a/libstdc++-v3/src/filesystem/ops.cc b/libstdc++-v3/src/filesystem/ops.cc
index 5ff8120f6076d61dca814754bab18775c65a1f02..7b261fb93aae09d237584a0e62b1f63ff71ff6ca 100644 (file)
--- a/libstdc++-v3/src/filesystem/ops.cc
+++ b/libstdc++-v3/src/filesystem/ops.cc
@@ -116,6 +116,7 @@ fs::canonical(const path& p, const path& base, error_code& ec)
 {
   const path pa = absolute(p, base);
   path result;
+
 #ifdef _GLIBCXX_USE_REALPATH
   char_ptr buf{ nullptr };
 # if _XOPEN_VERSION < 700
@@ -137,18 +138,9 @@ fs::canonical(const path& p, const path& base, error_code& ec)
     }
 #endif
 
-  auto fail = [&ec, &result](int e) mutable {
-      if (!ec.value())
-       ec.assign(e, std::generic_category());
-      result.clear();
-  };
-
   if (!exists(pa, ec))
-    {
-      fail(ENOENT);
-      return result;
-    }
-  // else we can assume no unresolvable symlink loops
+    return result;
+  // else: we know there are (currently) no unresolvable symlink loops
 
   result = pa.root_path();
 
@@ -156,20 +148,19 @@ fs::canonical(const path& p, const path& base, error_code& ec)
   for (auto& f : pa.relative_path())
     cmpts.push_back(f);
 
-  while (!cmpts.empty())
+  int max_allowed_symlinks = 40;
+
+  while (!cmpts.empty() && !ec)
     {
       path f = std::move(cmpts.front());
       cmpts.pop_front();
 
-      if (f.compare(".") == 0)
+      if (is_dot(f))
        {
-         if (!is_directory(result, ec))
-           {
-             fail(ENOTDIR);
-             break;
-           }
+         if (!is_directory(result, ec) && !ec)
+           ec.assign(ENOTDIR, std::generic_category());
        }
-      else if (f.compare("..") == 0)
+      else if (is_dotdot(f))
        {
          auto parent = result.parent_path();
          if (parent.empty())
@@ -184,27 +175,30 @@ fs::canonical(const path& p, const path& base, error_code& ec)
          if (is_symlink(result, ec))
            {
              path link = read_symlink(result, ec);
-             if (!ec.value())
+             if (!ec)
                {
-                 if (link.is_absolute())
+                 if (--max_allowed_symlinks == 0)
+                   ec.assign(ELOOP, std::generic_category());
+                 else
                    {
-                     result = link.root_path();
-                     link = link.relative_path();
+                     if (link.is_absolute())
+                       {
+                         result = link.root_path();
+                         link = link.relative_path();
+                       }
+                     else
+                       result.remove_filename();
+
+                     cmpts.insert(cmpts.begin(), link.begin(), link.end());
                    }
-                 else
-                   result.remove_filename();
-
-                 cmpts.insert(cmpts.begin(), link.begin(), link.end());
                }
            }
-
-         if (ec.value() || !exists(result, ec))
-           {
-             fail(ENOENT);
-             break;
-           }
        }
     }
+
+  if (ec || !exists(result, ec))
+    result.clear();
+
   return result;
 }