diff --git a/doc/5.4_dataflow_analysis.md b/doc/5.4_dataflow_analysis.md
index 840b4f3..2516c98 100644
--- a/doc/5.4_dataflow_analysis.md
+++ b/doc/5.4_dataflow_analysis.md
@@ -204,3 +204,64 @@ p = *q;
 
 
 ## 实例分析
+#### 检测指针变量的错误使用
+在检测指针变量的错误使用时，我们关心的是变量的状态。
+
+下面看一个例子：
+```c
+int contrived(int *p, int *w, int x) {
+    int *q;
+    if (x) {
+        kfree(w); // w free
+        q = p;
+    }
+    [...]
+    if (!x)
+        return *w;
+    return *q;  // p use after free
+}
+int contrived_caller(int *w, int x, int *p) {
+    kfree(p);   // p free
+    [...]
+    int r = contrived(p, w, x);
+    [...]
+    return *w;  // w use after free
+}
+```
+可以看到上面的代码可能出现 use-after-free 漏洞。
+
+这里我们采用路径敏感的数据流分析，控制流图如下：
+
+![](../pic/5.4_cfg1.png)
+![](../pic/5.4_cfg2.png)
+
+调用图如下：
+
+![](../pic/5.4_cg1.png)
+
+下面是用于检测指针变量错误使用的检测规则：
+```
+v 被分配空间 ==> v.start
+v.start: {kfree(v)} ==> v.free
+v.free: {*v} ==> v.useAfterFree
+v.free: {kfree(v)} ==> v.doubleFree
+```
+
+分析过程从函数 contrived_call 的入口点开始，对于过程内代码的分析，使用深度优先遍历控制流图的方法，并使用基本块摘要进行辅助，而对于过程间的分析，选择在遇到函数调用时直接分析被调用函数内代码的方式，并使用函数摘要。
+
+函数 contrived 中的路径有两条：
+- BB0->BB1->BB2->BB3->BB5->BB6：在进行到 BB5 时，BB5 的前置条件为 p.free, q.free 和 w.free，此时语句 `q1 = *q` 将触发 use-after-free 规则并设置 q.useAfterFree 状态。然后返回到函数 contrived_call 的 BB2，其前置条件为 p.useAfterFree, w.free，此时语句 `w1 = *w` 设置 w.useAfterFree。
+- BB0->BB1->BB3->BB4->BB6：该路径是安全的。
+
+#### 检测缓冲区溢出
+在检测缓冲区溢出时，我们关心的是变量的取值，并在一些预定义的敏感操作所在的程序点上，对变量的取值进行检查。
+
+下面是一些记录变量的取值的规则：
+```
+char s[n];            // len(s) = n
+strcpy(des, src);     // len(des) > len(src)
+strncpy(des, src, n); // len(des) > min(len(src), n)
+s = "foo";            // len(s) = 4
+strcat(s, suffix);    // len(s) = len(s) + len(suffix) - 1
+fgets(s, n, ...);     // len(s) > n
+```
diff --git a/pic/5.4_cfg1.png b/pic/5.4_cfg1.png
new file mode 100644
index 0000000..a9df3a7
Binary files /dev/null and b/pic/5.4_cfg1.png differ
diff --git a/pic/5.4_cfg2.png b/pic/5.4_cfg2.png
new file mode 100644
index 0000000..69d1748
Binary files /dev/null and b/pic/5.4_cfg2.png differ
diff --git a/pic/5.4_cg1.png b/pic/5.4_cg1.png
new file mode 100644
index 0000000..fd76121
Binary files /dev/null and b/pic/5.4_cg1.png differ
diff --git a/pic/5.4_state.png b/pic/5.4_state.png
index 1179e50..cb700a7 100644
Binary files a/pic/5.4_state.png and b/pic/5.4_state.png differ
diff --git a/src/Others/5.4_dataflow_analysis/cfg1.gv b/src/Others/5.4_dataflow_analysis/cfg1.gv
new file mode 100644
index 0000000..655a6d6
--- /dev/null
+++ b/src/Others/5.4_dataflow_analysis/cfg1.gv
@@ -0,0 +1,22 @@
+digraph {
+	labelloc = "title";
+	label = "int contrived(int *p, int *w, int x)";
+	node [shape="record"];
+
+	bb0 [label="BB0"];
+	bb1 [label="BB1: if(x)"];
+	bb2 [label="BB2: param w"];
+	bb3 [label="BB3: x1 =! x"];
+	bb4 [label="BB4: w1 = *w"];
+	bb5 [label="BB5: q1 = *q"];
+	bb6 [label="BB6"];
+
+	bb0 -> bb1;
+	bb1 -> bb2;
+	bb1 -> bb3;
+	bb2 -> bb3;
+	bb3 -> bb4;
+	bb3 -> bb5;
+	bb4 -> bb6;
+	bb5 -> bb6;
+}
\ No newline at end of file
diff --git a/src/Others/5.4_dataflow_analysis/cfg2.gv b/src/Others/5.4_dataflow_analysis/cfg2.gv
new file mode 100644
index 0000000..10f8f37
--- /dev/null
+++ b/src/Others/5.4_dataflow_analysis/cfg2.gv
@@ -0,0 +1,20 @@
+digraph {
+	labelloc = "title";
+	label = "int contrived_caller(int *w, int x, int *p)";
+	node [shape="record"];
+
+	bb0 [label="BB0"];
+	bb1 [label="BB1: param p\n
+		call kfree\n
+		param p\n
+		param w\n
+		param\n
+		call contrived"];
+	bb2 [label="BB2: r = ret\n
+		w1 = *w"];
+	bb3 [label="BB3"];
+
+	bb0 -> bb1;
+	bb1 -> bb2;
+	bb2 -> bb3;
+}
\ No newline at end of file
diff --git a/src/Others/5.4_dataflow_analysis/cg.gv b/src/Others/5.4_dataflow_analysis/cg.gv
new file mode 100644
index 0000000..2074a15
--- /dev/null
+++ b/src/Others/5.4_dataflow_analysis/cg.gv
@@ -0,0 +1,9 @@
+digraph {
+	0 [label="contrived_caller"];
+	1 [label="contrived"];
+	2 [label="kfree"];
+
+	0 -> 1;
+	0 -> 2;
+	1 -> 2;
+}
\ No newline at end of file
diff --git a/src/Others/5.4_dataflow_analysis/sm.gv b/src/Others/5.4_dataflow_analysis/sm.gv
new file mode 100644
index 0000000..e447064
--- /dev/null
+++ b/src/Others/5.4_dataflow_analysis/sm.gv
@@ -0,0 +1,10 @@
+digraph {
+	0 [style="filled"];
+	2 [shape="doublecircle"];
+	3 [shape="doublecircle"];
+
+	0 -> 2 [label="被使用"];
+	0 -> 3 [label="释放"];
+	0 -> 1 [label="释放"];
+	1 -> 0 [label="分配"];
+}
\ No newline at end of file