[HWASAN] Fix TLS + signal handling related crash

[kstoimenov]

Summary

When a signal is raised before HWASAN has a chance to initialize it's TLS entry the program crashes. This only happens when hwasan-with-tls is true, which is default value. This patch fixes the problem by disabling signals during thread initialization time.

[vitalybuka]

It would be awesome to have a test, but here D113328 I failed to make reproducer for the similar patch.

compiler-rt/lib/hwasan/hwasan_interceptors.cpp

48–49

Up to you, but I guess you still can keep *A = {callback, param};
it should zero initialize the tail

48–49

for consistency, as it makes no difference with the current state of code
I'd either remove { }, or move block under {}

[vitalybuka]

the description formatting as is will not look good in "git log"

[vitalybuka]

compiler-rt/lib/hwasan/hwasan_interceptors.cpp

47–48

unrelated to the patch, but this could be a source of subtle leaks

Imagine:

1. caller allocate param on head
2. pass it into pthread_create
3. forget the pointer
4. Lsan checks for leaks
5. HwasanThreadStartFunc executed

so if lsan checks in the step 4, heap allocated param pointer is only in the mapped region, which lsan can't see, and
before __hwasan_thread_enter the new thread is not visible to lsan as well

[kstoimenov]

Addressed comments.

compiler-rt/lib/hwasan/hwasan_interceptors.cpp

 //===-- hwasan_interceptors.cpp -------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of HWAddressSanitizer.
 //
 // Interceptors for standard library functions.
 //
 // FIXME: move as many interceptors as possible into
 // sanitizer_common/sanitizer_common_interceptors.h
 //===----------------------------------------------------------------------===//
 
-#include "interception/interception.h"
 #include "hwasan.h"
 #include "hwasan_thread.h"
+#include "interception/interception.h"
+#include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 
 #if !SANITIZER_FUCHSIA
 
 using namespace __hwasan;
 
 #if HWASAN_WITH_INTERCEPTORS
 
 struct ThreadStartArg {
   thread_callback_t callback;
   void *param;
+  __sanitizer_sigset_t starting_sigset_;
 };
 
 static void *HwasanThreadStartFunc(void *arg) {
   __hwasan_thread_enter();
   ThreadStartArg A = *reinterpret_cast<ThreadStartArg*>(arg);
+  SetSigProcMask(&A.starting_sigset_, nullptr);
   UnmapOrDie(arg, GetPageSizeCached());
   return A.callback(A.param);
 }
 
 INTERCEPTOR(int, pthread_create, void *th, void *attr, void *(*callback)(void*),
             void * param) {
   EnsureMainThreadIDIsCorrect();
   ScopedTaggingDisabler tagging_disabler;
   ThreadStartArg *A = reinterpret_cast<ThreadStartArg *> (MmapOrDie(
       GetPageSizeCached(), "pthread_create"));
-  *A = {callback, param};
-  int res;
-  {
-    // ASAN uses the same approach to disable leaks from pthread_create.
+  A->callback = callback;
+  A->param = param;
+  ScopedBlockSignals block(&A->starting_sigset_);
 #    if CAN_SANITIZE_LEAKS
-    __lsan::ScopedInterceptorDisabler lsan_disabler;
 #    endif
-    res = REAL(pthread_create)(th, attr, &HwasanThreadStartFunc, A);
-  }
-  return res;
+  return REAL(pthread_create)(th, attr, &HwasanThreadStartFunc, A);
 }
 
 INTERCEPTOR(int, pthread_join, void *t, void **arg) {
   return REAL(pthread_join)(t, arg);
 }
 
 DEFINE_REAL_PTHREAD_FUNCTIONS