[compiler-rt] r316589 - [asan] Don't print rows of shadow bytes outside shadow memory

[Reid Kleckner via llvm-commits]

Author: rnk
Date: Wed Oct 25 09:54:12 2017
New Revision: 316589

URL: http://llvm.org/viewvc/llvm-project?rev=316589&view=rev
Log:
[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

Modified:
    compiler-rt/trunk/lib/asan/asan_errors.cc

Modified: compiler-rt/trunk/lib/asan/asan_errors.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_errors.cc?rev=316589&r1=316588&r2=316589&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_errors.cc (original)
+++ compiler-rt/trunk/lib/asan/asan_errors.cc Wed Oct 25 09:54:12 2017
@@ -422,9 +422,14 @@ static void PrintShadowMemoryForAddress(
   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());