[asan] Don't print rows of shadow bytes outside shadow memory

Summary:
They might not be mapped on some platforms such as Win64.  In
particular, this happens if the user address is null. There will not be
any shadow memory 5*16 bytes before the user address. This happens on
Win64 in the error_report_callback.cc test case. It's not clear why this
isn't a problem on Linux as well.

Fixes PR35058

Reviewers: vitalybuka

Subscribers: kubamracek, llvm-commits

Differential Revision: https://reviews.llvm.org/D39260

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@316589 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 2 deletions

diff --git a/lib/asan/asan_errors.cc b/lib/asan/asan_errors.cc
index d42a86850..dee666d54 100644
--- a/lib/asan/asan_errors.cc
+++ b/lib/asan/asan_errors.cc
@@ -422,9 +422,14 @@ static void PrintShadowMemoryForAddress(uptr addr) {
   InternalScopedString str(4096 * 8);
   str.append("Shadow bytes around the buggy address:\n");
   for (int i = -5; i <= 5; i++) {
+    uptr row_shadow_addr = aligned_shadow + i * n_bytes_per_row;
+    // Skip rows that would be outside the shadow range. This can happen when
+    // the user address is near the bottom, top, or shadow gap of the address
+    // space.
+    if (!AddrIsInShadow(row_shadow_addr)) continue;
     const char *prefix = (i == 0) ? "=>" : "  ";
-    PrintShadowBytes(&str, prefix, (u8 *)(aligned_shadow + i * n_bytes_per_row),
-                     (u8 *)shadow_addr, n_bytes_per_row);
+    PrintShadowBytes(&str, prefix, (u8 *)row_shadow_addr, (u8 *)shadow_addr,
+                     n_bytes_per_row);
   }
   if (flags()->print_legend) PrintLegend(&str);
   Printf("%s", str.data());