[sanitizer] When setting up shadow memory on iOS, fix handling the return value of task_info on older OS versions

task_vm_info is a "revisioned" structure, new OS versions add fields to the end, and compatibility is based on the reported size. On older OS versions, min_address/max_address is not filled back. Let's handle that case. Unfortunately, we can't really write a test (as the failure only happens when on a specific OS version).

Differential Revision: https://reviews.llvm.org/D50275

llvm-svn: 340058

1 files changed, 2 insertions, 2 deletions

diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
index 180d7c199ae..48747bc8359 100644
--- a/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_mac.cc
@@ -890,10 +890,10 @@ struct __sanitizer_task_vm_info {
     (sizeof(__sanitizer_task_vm_info) / sizeof(natural_t)))
 
 uptr GetTaskInfoMaxAddress() {
-  __sanitizer_task_vm_info vm_info = {};
+  __sanitizer_task_vm_info vm_info = {} /* zero initialize */;
   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);
-  if (err == 0) {
+  if (err == 0 && vm_info.max_address != 0) {
     return vm_info.max_address - 1;
   } else {
     // xnu cannot provide vm address limit