[tsan] Check for pvalloc overlow

[cryptoad]

Summary

CheckForPvallocOverflow was introduced with D35818 to detect when pvalloc
would wrap when rounding up to the next multiple of the page size.

Add this check to TSan's pvalloc implementation.

[cryptoad]

Abandoning for now, while I check what's causing the MSan errors.

lib/tsan/rtl/tsan_mman.cc

 }
 
 void *user_valloc(ThreadState *thr, uptr pc, uptr sz) {
   return SetErrnoOnNull(user_alloc_internal(thr, pc, sz, GetPageSizeCached()));
 }
 
 void *user_pvalloc(ThreadState *thr, uptr pc, uptr sz) {
   uptr PageSize = GetPageSizeCached();
+  if (UNLIKELY(CheckForPvallocOverflow(sz, PageSize))) {
+    errno = errno_ENOMEM;
+    return Allocator::FailureHandler::OnBadRequest();
+  }
   // pvalloc(0) should allocate one page.
   sz = sz ? RoundUpTo(sz, PageSize) : PageSize;
   return SetErrnoOnNull(user_alloc_internal(thr, pc, sz, PageSize));
 }
 
 uptr user_alloc_usable_size(const void *p) {
   if (p == 0)
     return 0;

lib/tsan/tests/unit/tsan_mman_test.cc

TEST(Mman, Stats) {
   EXPECT_EQ(alloc0, __sanitizer_get_current_allocated_bytes());
   EXPECT_GE(__sanitizer_get_heap_size(), heap0);
   EXPECT_EQ(free0, __sanitizer_get_free_bytes());
   EXPECT_EQ(unmapped0, __sanitizer_get_unmapped_bytes());
 }
 
 TEST(Mman, Valloc) {
   ThreadState *thr = cur_thread();
+  uptr page_size = GetPageSizeCached();
 
   void *p = user_valloc(thr, 0, 100);
   EXPECT_NE(p, (void*)0);
   user_free(thr, 0, p);
 
   p = user_pvalloc(thr, 0, 100);
   EXPECT_NE(p, (void*)0);
   user_free(thr, 0, p);
 
   p = user_pvalloc(thr, 0, 0);
   EXPECT_NE(p, (void*)0);
-  EXPECT_EQ(GetPageSizeCached(), __sanitizer_get_allocated_size(p));
+  EXPECT_EQ(page_size, __sanitizer_get_allocated_size(p));
   user_free(thr, 0, p);
+
+  EXPECT_DEATH(p = user_pvalloc(thr, 0, (uptr)-page_size),
+               "allocator is terminating the process instead of returning 0");
+  EXPECT_DEATH(p = user_pvalloc(thr, 0, (uptr)-1),
+               "allocator is terminating the process instead of returning 0");
 }
 
 #if !SANITIZER_DEBUG
 // EXPECT_DEATH clones a thread with 4K stack,
 // which is overflown by tsan memory accesses functions in debug mode.
 
 TEST(Mman, CallocOverflow) {
   ThreadState *thr = cur_thread();