[Msan] Check returning value of DTLS_Get()

[kutuzov.viktor.84]

Summary

DTLS_Get() returns 0 if SANITIZER_INTERCEPT_TLS_GET_ADDR expands to zero value.

[kcc]

LGTM

Closed by commit rL222818 (authored by vkutuzov).

lib/msan/msan_thread.cc

void MsanThread::SetThreadStackAndTls() {
   CHECK(AddrIsInStack((uptr)&local));
 }
 
 void MsanThread::ClearShadowForThreadStackAndTLS() {
   __msan_unpoison((void *)stack_bottom_, stack_top_ - stack_bottom_);
   if (tls_begin_ != tls_end_)
     __msan_unpoison((void *)tls_begin_, tls_end_ - tls_begin_);
   DTLS *dtls = DTLS_Get();
+  CHECK_NE(dtls, 0);
   for (uptr i = 0; i < dtls->dtv_size; ++i)
     __msan_unpoison((void *)(dtls->dtv[i].beg), dtls->dtv[i].size);
 }
 
 void MsanThread::Init() {
   SetThreadStackAndTls();
   CHECK(MEM_IS_APP(stack_bottom_));
   CHECK(MEM_IS_APP(stack_top_ - 1));