diff --git a/linker/linker_cfi.cpp b/linker/linker_cfi.cpp
index 5995013..87b5d34 100644
--- a/linker/linker_cfi.cpp
+++ b/linker/linker_cfi.cpp
@@ -56,6 +56,7 @@
         reinterpret_cast<char*>(mmap(nullptr, aligned_end - aligned_start, PROT_READ | PROT_WRITE,
                                      MAP_PRIVATE | MAP_ANONYMOUS, -1, 0));
     CHECK(tmp_start != MAP_FAILED);
+    mprotect(aligned_start, aligned_end - aligned_start, PROT_READ);
     memcpy(tmp_start, aligned_start, shadow_start - aligned_start);
     memcpy(tmp_start + (shadow_end - aligned_start), shadow_end, aligned_end - shadow_end);
   }
@@ -154,7 +155,7 @@
 
 uintptr_t CFIShadowWriter::MapShadow() {
   void* p =
-      mmap(nullptr, kShadowSize, PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
+      mmap(nullptr, kShadowSize, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE, -1, 0);
   CHECK(p != MAP_FAILED);
   return reinterpret_cast<uintptr_t>(p);
 }