Fix overflow issue in Zone::New
When requesting a large allocation near the end of the address space,
the computation could overflow and erroneously *not* grow the Zone
as required.
BUG=chromium:606115
LOG=y
Review-Url: https://codereview.chromium.org/1930873002
Cr-Commit-Position: refs/heads/master@{#35903}
diff --git a/src/zone.cc b/src/zone.cc
index 461ee73..a10b636 100644
--- a/src/zone.cc
+++ b/src/zone.cc
@@ -104,7 +104,10 @@
Address result = position_;
const size_t size_with_redzone = size + kASanRedzoneBytes;
- if (limit_ < position_ + size_with_redzone) {
+ const uintptr_t limit = reinterpret_cast<uintptr_t>(limit_);
+ const uintptr_t position = reinterpret_cast<uintptr_t>(position_);
+ // position_ > limit_ can be true after the alignment correction above.
+ if (limit < position || size_with_redzone > limit - position) {
result = NewExpand(size_with_redzone);
} else {
position_ += size_with_redzone;
@@ -221,7 +224,10 @@
// Make sure the requested size is already properly aligned and that
// there isn't enough room in the Zone to satisfy the request.
DCHECK_EQ(size, RoundDown(size, kAlignment));
- DCHECK_LT(limit_, position_ + size);
+ DCHECK(limit_ < position_ ||
+ reinterpret_cast<uintptr_t>(limit_) -
+ reinterpret_cast<uintptr_t>(position_) <
+ size);
// Compute the new segment size. We use a 'high water mark'
// strategy, where we increase the segment size every time we expand
