From 48c9175fe5260e03ecdb7a641ae06b813cc7701d Mon Sep 17 00:00:00 2001
From: Adrian Prantl <aprantl@apple.com>
Date: Mon, 23 Apr 2018 16:08:01 +0000
Subject: [PATCH] Fix computeSymbolSizes SEGFAULT on invalid file

We use llvm-symbolizer in some production systems, and we run it
against all possibly related files, including some that are not
ELF. We noticed that for some of those invalid files, llvm-symbolizer
would crash with SEGFAULT. Here is an example of such a file.

It is due to that in computeSymbolSizes, a loop uses condition

  for (unsigned I = 0, N = Addresses.size() - 1; I < N; ++I) {

where if Addresses.size() is 0, N would overflow and causing the loop
to access invalid memory.

Instead of patching the loop conditions, the commit makes so that the
function returns early if Addresses is empty.

Validated by checking that llvm-symbolizer no longer crashes.

Patch by Teng Qin!

Differential Revision: https://reviews.llvm.org/D44285

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@330610 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Object/SymbolSize.cpp           | 4 ++++
 test/tools/llvm-symbolizer/sym.test | 6 +++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/Object/SymbolSize.cpp b/lib/Object/SymbolSize.cpp
index dd49d5f116b..004fb1b0754 100644
--- a/lib/Object/SymbolSize.cpp
+++ b/lib/Object/SymbolSize.cpp
@@ -66,6 +66,10 @@ llvm::object::computeSymbolSizes(const ObjectFile &O) {
     Addresses.push_back(
         {O.symbol_end(), Address + Size, 0, getSectionID(O, Sec)});
   }
+
+  if (Addresses.empty())
+    return Ret;
+
   array_pod_sort(Addresses.begin(), Addresses.end(), compareAddress);
 
   // Compute the size as the gap to the next symbol
diff --git a/test/tools/llvm-symbolizer/sym.test b/test/tools/llvm-symbolizer/sym.test
index 27f06901ff6..871c16a494c 100644
--- a/test/tools/llvm-symbolizer/sym.test
+++ b/test/tools/llvm-symbolizer/sym.test
@@ -19,6 +19,8 @@
 
 RUN: llvm-symbolizer -print-address -obj=%p/Inputs/addr.exe < %p/Inputs/addr.inp | FileCheck %s
 RUN: llvm-symbolizer -inlining -print-address -pretty-print -obj=%p/Inputs/addr.exe < %p/Inputs/addr.inp | FileCheck --check-prefix="PRETTY" %s 
+RUN: echo "0x1" > %t.input
+RUN: llvm-symbolizer -obj=%p/Inputs/zero < %t.input | FileCheck --check-prefix="ZERO" %s
 
 #CHECK: some text
 #CHECK: 0x40054d
@@ -31,4 +33,6 @@ RUN: llvm-symbolizer -inlining -print-address -pretty-print -obj=%p/Inputs/addr.
 #PRETTY:  (inlined by) inc at {{[/\]+}}tmp{{[/\]+}}x.c:7:0
 #PRETTY   (inlined by) main at {{[/\]+}}tmp{{[/\]+}}x.c:14:0
 #PRETTY: some text2
-
+#
+#ZERO: ??
+#ZERO: ??:0:0
-- 
2.11.0