[compiler-rt] check max address from kernel is <= mmap range size

[aralisza]

Summary

If these sizes do not match, asan will not work as expected. Previously, we added compile-time checks for non-iOS platforms. We check at run time for iOS because we get the max VM size from the kernel at run time.

rdar://76477969

[aralisza]

-1

[aralisza]

rebase

[delcypher]

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

1188

Suggestion. Add a variable explicitly document our intent. There's a risk that someone might change the return value but forget to change the runtime check.

if (max_vm != 0) {
  const uptr ret_value = max_vm - 1;
  CHECK_LE(ret_value, SANITIZER_MMAP_RANGE_SIZE)
  return ret_value;
}

[aralisza]

assign ret value to const

[delcypher]

LGTM apart from the description. The description probably should mention this is the runtime counterpart to the previous patch that added static checks. We have to do this check at runtime because we get the VM size from the kernel at runtime.

compiler-rt/lib/sanitizer_common/sanitizer_mac.cpp

static uptr GetTaskInfoMaxAddress() {
   mach_msg_type_number_t count = __SANITIZER_TASK_VM_INFO_COUNT;
   int err = task_info(mach_task_self(), TASK_VM_INFO, (int *)&vm_info, &count);
   return err ? 0 : vm_info.max_address;
 }
 
 uptr GetMaxUserVirtualAddress() {
   static uptr max_vm = GetTaskInfoMaxAddress();
   if (max_vm != 0) {
-    return max_vm - 1;
+    const uptr ret_value = max_vm - 1;
+    CHECK_LE(ret_value, SANITIZER_MMAP_RANGE_SIZE);
+    return ret_value;
   }
 
   // xnu cannot provide vm address limit
 # if SANITIZER_WORDSIZE == 32
   constexpr uptr fallback_max_vm = 0xffe00000 - 1;
 # else
   constexpr uptr fallback_max_vm = 0x200000000 - 1;
 # endif