[PATCH] D69051: Handle libhwasan system allocator fallback during thread initialisation

[Matthew Malcomson via Phabricator via llvm-commits]

mmalcomson updated this revision to Diff 225655.
mmalcomson edited the summary of this revision.
mmalcomson added a comment.

Now avoid returning a zero tag when tagging is disabled.

I've avoided that by returning a fixed non-zero tag from Thread::GenerateRandomTag.

NOTE: There's the same basic problem of tagging with zero going to the system allocator free when setting HWASAN_OPTIONS `tag_in_malloc=false`.  I intend to fix that in a separate patch.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D69051/new/

https://reviews.llvm.org/D69051

Files:
  compiler-rt/lib/hwasan/hwasan_thread.cpp


Index: compiler-rt/lib/hwasan/hwasan_thread.cpp
===================================================================
--- compiler-rt/lib/hwasan/hwasan_thread.cpp
+++ compiler-rt/lib/hwasan/hwasan_thread.cpp
@@ -108,7 +108,15 @@
 
 // Generate a (pseudo-)random non-zero tag.
 tag_t Thread::GenerateRandomTag() {
-  if (tagging_disabled_) return 0;
+  // Return non-zero when tagging is not disabled so that the allocator
+  // fallback knows whatever pointer is being created has not come from the
+  // system allocator.
+  if (tagging_disabled_)
+#if HWASAN_WITH_INTERCEPTORS
+    return flags()->disable_allocator_tagging ? 0 : 0x10;
+#else
+    return 0;
+#endif
   tag_t tag;
   do {
     if (flags()->random_tags) {


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