[BugFix](function) fix reverse function dynamic buffer overflow due to illegal character

be/src/util/simd/vstring_function.h

@@ -20,6 +20,7 @@
 #include <unistd.h>
 
 #include <array>
+#include <cstddef>
 #include <cstdint>
 
 #ifdef __aarch64__
@@ -144,7 +145,15 @@ class VStringFunctions {
         } else {
             for (size_t i = 0, char_size = 0; i < str.len; i += char_size) {
                 char_size = UTF8_BYTE_LENGTH[(unsigned char)(str.ptr)[i]];
-                std::copy(str.ptr + i, str.ptr + i + char_size, dst.ptr + str.len - i - char_size);
+                // there exists occasion where the last character is an illegal UTF-8 one which returns
+                // a char_size larger than the actual space, which would cause offset execeeding the buffer range
+                // for example, consider str.len=4, i = 3, then the last char returns char_size 2, then
+                // the str.ptr + offset would exceed the buffer range
+                size_t offset = i + char_size;
+                if (offset > str.len) {
+                    offset = str.len;
+                }
+                std::copy(str.ptr + i, str.ptr + offset, dst.ptr + str.len - offset);
             }
         }
     }

regression-test/data/query_p0/sql_functions/string_functions/test_reverse.out

@@ -4,3 +4,6 @@
 fsnnygnaw
 kn@8jlnuy
 
+-- !select --
+4
+

regression-test/suites/query_p0/sql_functions/string_functions/test_reverse.groovy

@@ -17,5 +17,6 @@
 
 suite("test_reverse") {
     qt_select "select reverse(k7) from test_query_db.test order by k1"
+    qt_select "select length( cast(reverse( cast(unhex( cast(hex( cast(651603156 as bigint)) as varchar)) as varchar)) as varchar)) as c3"
 }