Add fork_canary.c

Author: r888800009

fork_canary

@@ -0,0 +1,38 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+// gcc fork_canary.c -o ./fork_canary
+int main(int argc, char **argv) {
+  size_t index;
+  size_t *i = &index;
+  int canary_offset = 0xd;
+
+  // fork()
+  pid_t pid = fork();
+  if (pid == -1) {
+    perror("fork");
+    exit(EXIT_FAILURE);
+  }
+
+  // if child
+  if (pid == 0) {
+    printf("child canary?");
+    scanf("%p", &index);
+
+    if (index == i[canary_offset])
+      puts("canary!");
+    else
+      puts("not canary!");
+
+  } else {
+    // if parent
+    printf("parent canary: %p\n", i[canary_offset]);
+    // wait for child
+    int status;
+    waitpid(pid, &status, 0);
+  }
+
+  char *buf[10];
+  gets(buf);
+}