Merge pull request #87 from haolianfu/perfect_fix_crash_on_iOS15

Fixed the crash on iOS 15 perfectly: changing vm prot according to wh…

Author: tditchek

fishhook.c

@@ -81,12 +81,13 @@ static int prepend_rebindings(struct rebindings_entry **rebindings_head,
   return 0;
 }
 
-static vm_prot_t get_protection(void *sectionStart) {
+#if 0
+static int get_protection(void *addr, vm_prot_t *prot, vm_prot_t *max_prot) {
   mach_port_t task = mach_task_self();
   vm_size_t size = 0;
-  vm_address_t address = (vm_address_t)sectionStart;
+  vm_address_t address = (vm_address_t)addr;
   memory_object_name_t object;
-#if __LP64__
+#ifdef __LP64__
   mach_msg_type_number_t count = VM_REGION_BASIC_INFO_COUNT_64;
   vm_region_basic_info_data_64_t info;
   kern_return_t info_ret = vm_region_64(
@@ -97,25 +98,28 @@ static vm_prot_t get_protection(void *sectionStart) {
   kern_return_t info_ret = vm_region(task, &address, &size, VM_REGION_BASIC_INFO, (vm_region_info_t)&info, &count, &object);
 #endif
   if (info_ret == KERN_SUCCESS) {
-    return info.protection;
-  } else {
-    return VM_PROT_READ;
+    if (prot != NULL)
+      *prot = info.protection;
+
+    if (max_prot != NULL)
+      *max_prot = info.max_protection;
+
+    return 0;
   }
+
+  return -1;
 }
+#endif
+
 static void perform_rebinding_with_section(struct rebindings_entry *rebindings,
                                            section_t *section,
                                            intptr_t slide,
                                            nlist_t *symtab,
                                            char *strtab,
                                            uint32_t *indirect_symtab) {
-  const bool isDataConst = strcmp(section->segname, SEG_DATA_CONST) == 0;
   uint32_t *indirect_symbol_indices = indirect_symtab + section->reserved1;
   void **indirect_symbol_bindings = (void **)((uintptr_t)slide + section->addr);
-  vm_prot_t oldProtection = VM_PROT_READ;
-  if (isDataConst) {
-    oldProtection = get_protection(rebindings);
-    mprotect(indirect_symbol_bindings, section->size, PROT_READ | PROT_WRITE);
-  }
+
   for (uint i = 0; i < section->size / sizeof(void *); i++) {
     uint32_t symtab_index = indirect_symbol_indices[i];
     if (symtab_index == INDIRECT_SYMBOL_ABS || symtab_index == INDIRECT_SYMBOL_LOCAL ||
@@ -128,33 +132,36 @@ static void perform_rebinding_with_section(struct rebindings_entry *rebindings,
     struct rebindings_entry *cur = rebindings;
     while (cur) {
       for (uint j = 0; j < cur->rebindings_nel; j++) {
-        if (symbol_name_longer_than_1 &&
-            strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) {
-          if (cur->rebindings[j].replaced != NULL &&
-              indirect_symbol_bindings[i] != cur->rebindings[j].replacement) {
+        if (symbol_name_longer_than_1 && strcmp(&symbol_name[1], cur->rebindings[j].name) == 0) {
+          kern_return_t err;
+
+          if (cur->rebindings[j].replaced != NULL && indirect_symbol_bindings[i] != cur->rebindings[j].replacement)
             *(cur->rebindings[j].replaced) = indirect_symbol_bindings[i];
+
+          /**
+           * 1. Moved the vm protection modifying codes to here to reduce the
+           *    changing scope.
+           * 2. Adding VM_PROT_WRITE mode unconditionally because vm_region
+           *    API on some iOS/Mac reports mismatch vm protection attributes.
+           * -- Lianfu Hao Jun 16th, 2021
+           **/
+          err = vm_protect (mach_task_self (), (uintptr_t)indirect_symbol_bindings, section->size, 0, VM_PROT_READ | VM_PROT_WRITE | VM_PROT_COPY);
+          if (err == KERN_SUCCESS) {
+            /**
+             * Once we failed to change the vm protection, we
+             * MUST NOT continue the following write actions!
+             * iOS 15 has corrected the const segments prot.
+             * -- Lionfore Hao Jun 11th, 2021
+             **/
+            indirect_symbol_bindings[i] = cur->rebindings[j].replacement;
           }
-          indirect_symbol_bindings[i] = cur->rebindings[j].replacement;
           goto symbol_loop;
         }
       }
       cur = cur->next;
     }
   symbol_loop:;
   }
-  if (isDataConst) {
-    int protection = 0;
-    if (oldProtection & VM_PROT_READ) {
-      protection |= PROT_READ;
-    }
-    if (oldProtection & VM_PROT_WRITE) {
-      protection |= PROT_WRITE;
-    }
-    if (oldProtection & VM_PROT_EXECUTE) {
-      protection |= PROT_EXEC;
-    }
-    mprotect(indirect_symbol_bindings, section->size, protection);
-  }
 }
 
 static void rebind_symbols_for_image(struct rebindings_entry *rebindings,