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<dt>Revision</dt> <dd><a href="http://trac.webkit.org/projects/webkit/changeset/186335">186335</a></dd>
<dt>Author</dt> <dd>carlosgc@webkit.org</dd>
<dt>Date</dt> <dd>2015-07-06 02:56:44 -0700 (Mon, 06 Jul 2015)</dd>
</dl>
<h3>Log Message</h3>
<pre>Merge <a href="http://trac.webkit.org/projects/webkit/changeset/184883">r184883</a> - Integer overflow in XLarge allocation (due to unchecked roundUpToMultipleOf)
https://bugs.webkit.org/show_bug.cgi?id=145385
Reviewed by Andreas Kling.
Added some checking to verify that round-up operations will not overflow
a size_t.
The simplest way to do this was to introduce a notion of xLargeMax, like
we have for smallMax, mediumMax, and largeMax. It's a bit surprising at
first to think that there is an xLargeMax, since xLarge is what we use
to handle the biggest things. But computers have limits, so it makes sense.
FWIW, TCMalloc used to have an xLargeMax too, which it called kMaxValidPages.
No test because this bug was found by code inspection and I don't know
of a practical way to convince WebKit to make an allocation this large.
* bmalloc/Allocator.cpp:
(bmalloc::Allocator::tryAllocate):
(bmalloc::Allocator::allocate):
(bmalloc::Allocator::reallocate):
(bmalloc::Allocator::allocateSlowCase): Check against xLargeMax to avoid
overflow when rounding up.
* bmalloc/BAssert.h: Added support for explicit crashing.
* bmalloc/Sizes.h:</pre>
<h3>Modified Paths</h3>
<ul>
<li><a href="#releasesWebKitGTKwebkit28SourcebmallocChangeLog">releases/WebKitGTK/webkit-2.8/Source/bmalloc/ChangeLog</a></li>
<li><a href="#releasesWebKitGTKwebkit28SourcebmallocbmallocAllocatorcpp">releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Allocator.cpp</a></li>
<li><a href="#releasesWebKitGTKwebkit28SourcebmallocbmallocBAsserth">releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/BAssert.h</a></li>
<li><a href="#releasesWebKitGTKwebkit28SourcebmallocbmallocSizesh">releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Sizes.h</a></li>
</ul>
</div>
<div id="patch">
<h3>Diff</h3>
<a id="releasesWebKitGTKwebkit28SourcebmallocChangeLog"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/bmalloc/ChangeLog (186334 => 186335)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/bmalloc/ChangeLog 2015-07-06 09:55:36 UTC (rev 186334)
+++ releases/WebKitGTK/webkit-2.8/Source/bmalloc/ChangeLog 2015-07-06 09:56:44 UTC (rev 186335)
</span><span class="lines">@@ -1,3 +1,34 @@
</span><ins>+2015-05-26 Geoffrey Garen <ggaren@apple.com>
+
+ Integer overflow in XLarge allocation (due to unchecked roundUpToMultipleOf)
+ https://bugs.webkit.org/show_bug.cgi?id=145385
+
+ Reviewed by Andreas Kling.
+
+ Added some checking to verify that round-up operations will not overflow
+ a size_t.
+
+ The simplest way to do this was to introduce a notion of xLargeMax, like
+ we have for smallMax, mediumMax, and largeMax. It's a bit surprising at
+ first to think that there is an xLargeMax, since xLarge is what we use
+ to handle the biggest things. But computers have limits, so it makes sense.
+
+ FWIW, TCMalloc used to have an xLargeMax too, which it called kMaxValidPages.
+
+ No test because this bug was found by code inspection and I don't know
+ of a practical way to convince WebKit to make an allocation this large.
+
+ * bmalloc/Allocator.cpp:
+ (bmalloc::Allocator::tryAllocate):
+ (bmalloc::Allocator::allocate):
+ (bmalloc::Allocator::reallocate):
+ (bmalloc::Allocator::allocateSlowCase): Check against xLargeMax to avoid
+ overflow when rounding up.
+
+ * bmalloc/BAssert.h: Added support for explicit crashing.
+
+ * bmalloc/Sizes.h:
+
</ins><span class="cx"> 2015-05-07 Geoffrey Garen <ggaren@apple.com>
</span><span class="cx">
</span><span class="cx"> Release assert in com.apple.WebKit.WebContent under JavaScriptCore: JSC::JSONProtoFuncStringify
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit28SourcebmallocbmallocAllocatorcpp"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Allocator.cpp (186334 => 186335)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Allocator.cpp 2015-07-06 09:55:36 UTC (rev 186334)
+++ releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Allocator.cpp 2015-07-06 09:56:44 UTC (rev 186335)
</span><span class="lines">@@ -59,8 +59,12 @@
</span><span class="cx"> if (size <= largeMax)
</span><span class="cx"> return allocate(size);
</span><span class="cx">
</span><del>- std::lock_guard<StaticMutex> lock(PerProcess<Heap>::mutex());
- return PerProcess<Heap>::get()->tryAllocateXLarge(lock, superChunkSize, roundUpToMultipleOf<xLargeAlignment>(size));
</del><ins>+ if (size <= xLargeMax) {
+ std::lock_guard<StaticMutex> lock(PerProcess<Heap>::mutex());
+ return PerProcess<Heap>::getFastCase()->tryAllocateXLarge(lock, superChunkSize, roundUpToMultipleOf<xLargeAlignment>(size));
+ }
+
+ return nullptr;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void* Allocator::allocate(size_t alignment, size_t size)
</span><span class="lines">@@ -93,18 +97,25 @@
</span><span class="cx"> }
</span><span class="cx"> }
</span><span class="cx">
</span><del>- size = std::max(largeMin, roundUpToMultipleOf<largeAlignment>(size));
- alignment = roundUpToMultipleOf<largeAlignment>(alignment);
- size_t unalignedSize = largeMin + alignment + size;
- if (unalignedSize <= largeMax && alignment <= largeChunkSize / 2) {
</del><ins>+ if (size <= largeMax && alignment <= largeMax) {
+ size = std::max(largeMin, roundUpToMultipleOf<largeAlignment>(size));
+ alignment = roundUpToMultipleOf<largeAlignment>(alignment);
+ size_t unalignedSize = largeMin + alignment + size;
+ if (unalignedSize <= largeMax && alignment <= largeChunkSize / 2) {
+ std::lock_guard<StaticMutex> lock(PerProcess<Heap>::mutex());
+ return PerProcess<Heap>::getFastCase()->allocateLarge(lock, alignment, size, unalignedSize);
+ }
+ }
+
+ if (size <= xLargeMax && alignment <= xLargeMax) {
+ size = roundUpToMultipleOf<xLargeAlignment>(size);
+ alignment = std::max(superChunkSize, alignment);
</ins><span class="cx"> std::lock_guard<StaticMutex> lock(PerProcess<Heap>::mutex());
</span><del>- return PerProcess<Heap>::getFastCase()->allocateLarge(lock, alignment, size, unalignedSize);
</del><ins>+ return PerProcess<Heap>::getFastCase()->allocateXLarge(lock, alignment, size);
</ins><span class="cx"> }
</span><span class="cx">
</span><del>- size = roundUpToMultipleOf<xLargeAlignment>(size);
- alignment = std::max(superChunkSize, alignment);
- std::lock_guard<StaticMutex> lock(PerProcess<Heap>::mutex());
- return PerProcess<Heap>::getFastCase()->allocateXLarge(lock, alignment, size);
</del><ins>+ BCRASH();
+ return nullptr;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> void* Allocator::reallocate(void* object, size_t newSize)
</span><span class="lines">@@ -242,7 +253,11 @@
</span><span class="cx"> if (size <= largeMax)
</span><span class="cx"> return allocateLarge(size);
</span><span class="cx">
</span><del>- return allocateXLarge(size);
</del><ins>+ if (size <= xLargeMax)
+ return allocateXLarge(size);
+
+ BCRASH();
+ return nullptr;
</ins><span class="cx"> }
</span><span class="cx">
</span><span class="cx"> } // namespace bmalloc
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit28SourcebmallocbmallocBAsserth"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/BAssert.h (186334 => 186335)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/BAssert.h 2015-07-06 09:55:36 UTC (rev 186334)
+++ releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/BAssert.h 2015-07-06 09:56:44 UTC (rev 186335)
</span><span class="lines">@@ -26,10 +26,14 @@
</span><span class="cx"> #ifndef BAssert_h
</span><span class="cx"> #define BAssert_h
</span><span class="cx">
</span><ins>+#define BCRASH() do { \
+ *(int*)0xbbadbeef = 0; \
+} while (0);
+
</ins><span class="cx"> #define BASSERT_IMPL(x) do { \
</span><span class="cx"> if (!(x)) \
</span><del>- *(int*)0xbbadbeef = 0; \
-} while(0);
</del><ins>+ BCRASH(); \
+} while (0);
</ins><span class="cx">
</span><span class="cx"> #define RELEASE_BASSERT(x) BASSERT_IMPL(x)
</span><span class="cx">
</span></span></pre></div>
<a id="releasesWebKitGTKwebkit28SourcebmallocbmallocSizesh"></a>
<div class="modfile"><h4>Modified: releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Sizes.h (186334 => 186335)</h4>
<pre class="diff"><span>
<span class="info">--- releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Sizes.h 2015-07-06 09:55:36 UTC (rev 186334)
+++ releases/WebKitGTK/webkit-2.8/Source/bmalloc/bmalloc/Sizes.h 2015-07-06 09:56:44 UTC (rev 186335)
</span><span class="lines">@@ -80,6 +80,7 @@
</span><span class="cx"> static const size_t largeMin = mediumMax;
</span><span class="cx">
</span><span class="cx"> static const size_t xLargeAlignment = vmPageSize;
</span><ins>+ static const size_t xLargeMax = std::numeric_limits<size_t>::max() - xLargeAlignment; // Make sure that rounding up to xLargeAlignment does not overflow.
</ins><span class="cx">
</span><span class="cx"> static const size_t freeListSearchDepth = 16;
</span><span class="cx"> static const size_t freeListGrowFactor = 2;
</span></span></pre>
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