commit 469016b2ba86f46fd0d3b4a9b7d42591dbc1d91f
author Stephen Hines <srhines@google.com> Wed Jan 22 17:50:41 2020 -0800
committer Treehugger Robot <treehugger-gerrit@google.com> Thu Jan 23 16:31:31 2020 +0000
tree 4561f438aa6f3ef8f8443386a6ed8e9306b23963
parent b78f919c658563a613bf0e2204bade5ad5058330

Don't pattern-init an unused variable that overallocates the stack

ART is intentionally walking to the stack top (lowest address), but the
pattern initialization is accidentally triggering a sanitizer failure
for an overflow. Removing the pattern initialization from that unused
(and uninitialized) variable restores the original functionality of
accessing every page of the available stack.

Fixes: 148125929
Bug: 131390872

Test: m checkbuild ASAN_OPTIONS=detect_leaks=0 SANITIZE_HOST=address
Change-Id: I2b1e8bdc44044e8165a14a8e7b36dd8616d4a5b3

runtime/thread.cc

diff --git a/runtime/thread.cc b/runtime/thread.cc
index c3e4afe..2319f89 100644
--- a/runtime/thread.cc
+++ b/runtime/thread.cc
@@ -790,7 +790,9 @@
 #else
           1u;
 #endif
-      volatile char space[kPageSize - (kAsanMultiplier * 256)];
+      // Keep space uninitialized as it can overflow the stack otherwise (should Clang actually
+      // auto-initialize this local variable).
+      volatile char space[kPageSize - (kAsanMultiplier * 256)] __attribute__((uninitialized));
       char sink ATTRIBUTE_UNUSED = space[zero];  // NOLINT
       // Remove tag from the pointer. Nop in non-hwasan builds.
       uintptr_t addr = reinterpret_cast<uintptr_t>(__hwasan_tag_pointer(space, 0));