Fixed an out-of-bounds access.

2 files changed, 8 insertions, 1 deletions

diff --git a/base/base_tests/string_utils_test.cpp b/base/base_tests/string_utils_test.cpp
index 4eccdbd0f1..f1e2dff2cc 100644
--- a/base/base_tests/string_utils_test.cpp
+++ b/base/base_tests/string_utils_test.cpp
@@ -582,6 +582,11 @@ UNIT_TEST(AlmostEqual)
   TEST(!AlmostEqual("MKAD, 600 km", "MKAD, 599 km", 2), ());
   TEST(!AlmostEqual("MKAD, 45-y kilometre", "MKAD, 46", 2), ());
   TEST(!AlmostEqual("ул. Героев Панфиловцев", "ул. Планерная", 2), ());
+
+  string small(10, '\0');
+  string large(1000, '\0');
+  TEST(AlmostEqual(small, large, large.length()), ());
+  TEST(AlmostEqual(large, small, large.length()), ());
 }
 
 UNIT_TEST(EditDistance)
diff --git a/base/string_utils.cpp b/base/string_utils.cpp
index af21d91290..5f26059688 100644
--- a/base/string_utils.cpp
+++ b/base/string_utils.cpp
@@ -1,6 +1,7 @@
 #include "base/assert.hpp"
 #include "base/string_utils.hpp"
 
+#include "std/algorithm.hpp"
 #include "std/cmath.hpp"
 #include "std/iomanip.hpp"
 #include "std/iterator.hpp"
@@ -310,7 +311,8 @@ bool AlmostEqual(string const & str1, string const & str2, size_t mismatchedCoun
 
   for (size_t i = 0; i <= mismatchedCount; ++i)
   {
-    mis = mismatch(mis.first, str1End, mis.second);
+    auto const end = mis.first + min(distance(mis.first, str1End), distance(mis.second, str2End));
+    mis = mismatch(mis.first, end, mis.second);
     if (mis.first == str1End && mis.second == str2End)
       return true;
     if (mis.first != str1End)