[lld] r363026 - ELF: Don't process the partition end marker during combineEhSections().

[Peter Collingbourne via llvm-commits]

Author: pcc
Date: Mon Jun 10 19:54:30 2019
New Revision: 363026

URL: http://llvm.org/viewvc/llvm-project?rev=363026&view=rev
Log:
ELF: Don't process the partition end marker during combineEhSections().

Otherwise the getPartition() accessor may return an OOB pointer. Found
using _GLIBCXX_DEBUG.

The error is benign (we never dereference the pointer for the end marker)
so this wasn't caught by e.g. the sanitizer bots.

Modified:
    lld/trunk/ELF/Writer.cpp

Modified: lld/trunk/ELF/Writer.cpp
URL: http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Writer.cpp?rev=363026&r1=363025&r2=363026&view=diff
==============================================================================
--- lld/trunk/ELF/Writer.cpp (original)
+++ lld/trunk/ELF/Writer.cpp Mon Jun 10 19:54:30 2019
@@ -178,7 +178,9 @@ template <class ELFT> static void copySe
 
 template <class ELFT> static void combineEhSections() {
   for (InputSectionBase *&S : InputSections) {
-    if (!S->isLive())
+    // Ignore dead sections and the partition end marker (.part.end),
+    // whose partition number is out of bounds.
+    if (!S->isLive() || S->Partition == 255)
       continue;
 
     Partition &Part = S->getPartition();
@@ -442,7 +444,7 @@ template <class ELFT> static void create
   if (Partitions.size() != 1) {
     // Create the partition end marker. This needs to be in partition number 255
     // so that it is sorted after all other partitions. It also has other
-    // special handling (see createPhdrs()).
+    // special handling (see createPhdrs() and combineEhSections()).
     In.PartEnd = make<BssSection>(".part.end", Config->MaxPageSize, 1);
     In.PartEnd->Partition = 255;
     Add(In.PartEnd);