[TSan][Darwin] Make malloc_size interceptor more robust

[yln]

Summary

Previously we would crash in the TSan runtime if the user program passes
a pointer to malloc_size() that doesn't point into app memory.

In these cases, malloc_size() should return 0.

For ASan, we fixed a similar issue here:
https://reviews.llvm.org/D15008

Radar-Id: rdar://problem/86213149

[delcypher]

LGTM

compiler-rt/lib/tsan/rtl/tsan_mman.cpp

if (UNLIKELY(CheckForPvallocOverflow(sz, PageSize))) {
     ReportPvallocOverflow(sz, &stack);
   }
   // 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)
+  if (p == 0 || !IsAppMem((uptr)p))
     return 0;
   MBlock *b = ctx->metamap.GetBlock((uptr)p);
   if (!b)
     return 0;  // Not a valid pointer.
   if (b->siz == 0)
     return 1;  // Zero-sized allocations are actually 1 byte.
   return b->siz;
 }

compiler-rt/test/tsan/Darwin/malloc_size.mm

 // Test that malloc_zone_from_ptr returns a valid zone for a 0-sized allocation.
+// Test that malloc_size does not crash for an invalid pointer.
 
 // RUN: %clang_tsan %s -o %t -framework Foundation
 // RUN: %run %t 2>&1 | FileCheck %s
 
 #include <malloc/malloc.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sys/mman.h>
if (!p) {
     fprintf(stderr, "mmap failed\n");
     exit(1);
   }
   s = malloc_size(p);
   fprintf(stderr, "size = 0x%zx\n", s);
   // CHECK: size = 0x0
   describe_zone(p);
   // CHECK: zone = no zone
+
+  p = (void *)0x42;  // invalid pointer
+  s = malloc_size(p);
+  fprintf(stderr, "size = 0x%zx\n", s);
+  // CHECK: size = 0x0
+  describe_zone(p);
+  // CHECK: zone = no zone
+
+  return 0;
 }